In most cases a part of your computer get too hot or a windows hardware driver crash.
Are your drivers up-to-date?
What kind of video files do you want to convert? Do you have further details of the sourcefile (video/audio format, codec, resolution, bitrate, etc.). Which settings do you use for conversion?

The best way is to copy the active log from handbrake to see these informations.
You will see it, if you start your computer after the crash and open handbrake again.

I get a crash with handbrake, too. Sometimes the cpu usage is very high (100%) and the computer get very warm.
Then it is usefull to limit the max cpu usage to 50-80 % for testing and to reduce the cpu heat.
You can set it in the windows task manager. Choose the handbrake task in the list and with a right mouse click you get the settings for handbrake.

There you can see the number of cpu cores, which are used. The standard settings use all. To reduce the cpu-usage I remove some cpu cores from the list.
If handbrake works stable, your cpu or other things get to hot and crash the system.

I tried to convert a mkv video in a mkv video with lower resolution, to reduce its size. Last file I've tried was 1280x528, 23,98 Fps, SDR (8-bit 4:2:0, 1-1-1), 2 audio tracks , 4 subtitles tracks. I tried to convert in 720p HD, but PC reboots!

Log last trying:

HandBrake 1.7.3 (2024021000)
OS: Microsoft Windows NT 10.0.22631.0
CPU: 13th Gen Intel(R) Core(TM) i5-13400T
Ram: 7846 MB,
GPU Information:
Intel(R) UHD Graphics 730 - 31.0.101.3790
Screen: 1920x1080
Temp Dir: C:\Users\commerciale01\AppData\Local\Temp
Install Dir: C:\Program Files\HandBrake
Data Dir: C:\Users\commerciale01\AppData\Roaming\HandBrake

Starting Encode ...

[16:11:15] base preset: Fast 1080p30 (Modified)
[16:11:16] Remote Process started with Process ID: 11624 using port: 8037. Max Allowed Instances: 1
[16:11:16] Worker: Starting HandBrake Engine ...
[16:11:16] Worker: Parent Process Id 2752
[16:11:16] Worker: Starting Web Server on port 8037 ...
[16:11:16] Worker: Starting Listener: 1
[16:11:16] Worker: Server Started
[16:11:16] Worker: Disconnected worker monitoring enabled!
[16:11:16] Compile-time hardening features are enabled
Cannot load nvEncodeAPI64.dll
[16:11:16] vcn: not available on this system
[16:11:17] qsv: is available on this system
[16:11:17] hb_init: starting libhb thread
[16:11:17] Starting work at: Mon May 20 16:11:17 2024
[16:11:17] 1 job(s) to process
[16:11:17] json job:
{
"Audio": {
"AudioList": [
{
"Bitrate": 160,
"DRC": 0,
"Encoder": "av_aac",
"Gain": 0,
"Mixdown": 4,
"NormalizeMixLevel": false,
"Samplerate": 0,
"Name": "Ita Ac3 5.1",
"Track": 0,
"DitherMethod": 0
}
],
"CopyMask": [
"copy:aac"
],
"FallbackEncoder": "av_aac"
},
"Destination": {
"ChapterList": [
{
"Name": "Capitolo 1"
}
],
"ChapterMarkers": true,
"AlignAVStart": false,
"File": "C:\Users\commerciale01\Downloads\Killers Of The Flower Moon.mkv",
"Options": {
"IpodAtom": false,
"Optimize": false
},
"Mux": "av_mkv"
},
"Filters": {
"FilterList": [
{
"ID": 5,
"Settings": {
"mode": "7"
}
},
{
"ID": 4,
"Settings": {
"block-height": "16",
"block-thresh": "40",
"block-width": "16",
"filter-mode": "2",
"mode": "3",
"motion-thresh": "1",
"spatial-metric": "2",
"spatial-thresh": "1"
}
},
{
"ID": 19,
"Settings": {
"crop-bottom": "0",
"crop-left": "0",
"crop-right": "0",
"crop-top": "0",
"height": "528",
"width": "1280"
}
},
{
"ID": 10,
"Settings": {
"mode": "2",
"rate": "27000000/900000"
}
}
]
},
"PAR": {
"Num": 1,
"Den": 1
},
"Metadata": {
"Name": "MIRCrew"
},
"SequenceID": 0,
"Source": {
"Angle": 1,
"Range": {
"Type": "chapter",
"Start": 1,
"End": 1
},
"Title": 1,
"Path": "C:\Users\commerciale01\Downloads\Killers of the Flower Moon (2023) 720p H264 Ac3 5.1 Ita Eng Sub Ita Eng-MIRCrew.mkv",
"HWDecode": 6
},
"Subtitle": {
"Search": {
"Burn": true,
"Default": false,
"Enable": true,
"Forced": true
},
"SubtitleList": []
},
"Video": {
"Encoder": "x264",
"Level": "4.0",
"MultiPass": false,
"Turbo": false,
"ColorMatrixCode": 0,
"Options": "",
"Preset": "fast",
"Profile": "main",
"Quality": 22,
"QSV": {
"Decode": false
},
"HardwareDecode": 0
}
}
[16:11:17] CPU: 13th Gen Intel(R) Core(TM) i5-13400T
[16:11:17] - logical processor count: 16
[16:11:17] Intel Quick Sync Video support: yes, gpu list: 0
[16:11:17] Intel Quick Sync Video integrated adapter with index 0
[16:11:17] Impl mfx-gen library path: C:\Windows\System32\DriverStore\FileRepository\iigd_dch.inf_amd64_6ea18dcd92a33259\libmfx64-gen.dll
[16:11:17] - Intel Media SDK hardware: API 2.7 (minimum: 1.3)
[16:11:17] - Decode support: h264 hevc (8bit: yes, 10bit: yes) av1 (8bit: yes, 10bit: yes)
[16:11:17] - H.264 encoder: yes
[16:11:17] - preferred implementation: hardware (1) via D3D11
[16:11:17] - capabilities (hardware): lowpower breftype icq vsinfo chromalocinfo opt1 opt2+mbbrc+extbrc+trellis+repeatpps+ib_adapt+nmpslice
[16:11:17] - H.265 encoder: yes (8bit: yes, 10bit: yes)
[16:11:17] - preferred implementation: hardware (1) via D3D11
[16:11:17] - capabilities (hardware): lowpower bpyramid icq vsinfo masteringinfo cllinfo opt1
[16:11:17] - AV1 encoder: no
[16:11:17] hb_scan: path=C:\Users\commerciale01\Downloads\Killers of the Flower Moon (2023) 720p H264 Ac3 5.1 Ita Eng Sub Ita Eng-MIRCrew.mkv, title_index=1
Input #0, matroska,webm, from 'C:\Users\commerciale01\Downloads\Killers of the Flower Moon (2023) 720p H264 Ac3 5.1 Ita Eng Sub Ita Eng-MIRCrew.mkv':
Metadata:
title : MIRCrew
CREATION_TIME : 2024-03-10T12:19:33Z
ENCODER : Lavf55.12.0
Duration: 03:28:09.90, start: 0.078000, bitrate: 2592 kb/s
Stream #0:0(ita): Video: h264 (Main), yuv420p(tv, bt709, progressive), 1280x528, SAR 1:1 DAR 80:33, 23.98 fps, 23.98 tbr, 1k tbn (default)
Metadata:
title : MIRCrew
Stream #0:1(ita): Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s (default)
Metadata:
title : Ita Ac3 5.1
Stream #0:2(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s
Metadata:
title : Eng Ac3 5.1
Stream #0:3(ita): Subtitle: ass (default) (forced)
Metadata:
title : Forced ita
Stream #0:4(ita): Subtitle: ass
Metadata:
title : Ita
Stream #0:5(eng): Subtitle: ass
Metadata:
title : Ita
Stream #0:6(eng): Subtitle: ass
Metadata:
title : Eng
[16:11:17] scan: decoding previews for title 1
[16:11:17] scan: audio 0x1: ac3, rate=48000Hz, bitrate=384000 italiano (AC3, 5.1 ch, 384 kbps)
[16:11:17] scan: audio 0x2: ac3, rate=48000Hz, bitrate=384000 English (AC3, 5.1 ch, 384 kbps)
[16:11:17] scan: 10 previews, 1280x528, 23.976 fps, autocrop = 0/0/0/0, aspect 2.42:1, PAR 1:1, color profile: 1-1-1, chroma location: left
[16:11:17] scan: supported video decoders: avcodec qsv
[16:11:17] libhb: scan thread found 1 valid title(s)
[16:11:17] Skipping subtitle scan. No suitable subtitle tracks.
[16:11:17] Starting Task: Encoding Pass
[16:11:17] work: skipping crop/scale filter
[16:11:17] work: track 1, dithering not supported by codec
[16:11:17] work: only 1 chapter, disabling chapter markers
[16:11:17] job configuration:
[16:11:17] * source
[16:11:17] + C:\Users\commerciale01\Downloads\Killers of the Flower Moon (2023) 720p H264 Ac3 5.1 Ita Eng Sub Ita Eng-MIRCrew.mkv
[16:11:17] + title 1, chapter(s) 1 to 1
[16:11:17] + container: matroska,webm
[16:11:17] + data rate: 2592 kbps
[16:11:17] * destination
[16:11:17] + C:\Users\commerciale01\Downloads\Killers Of The Flower Moon.mkv
[16:11:17] + container: Matroska (libavformat)
[16:11:17] * video track
[16:11:17] + decoder: h264 8-bit (yuv420p)
[16:11:17] + filters
[16:11:17] + Comb Detect (mode=3:spatial-metric=2:motion-thresh=1:spatial-thresh=1:filter-mode=2:block-thresh=40:block-width=16:block-height=16)
[16:11:17] + Decomb (mode=39)
[16:11:17] + Framerate Shaper (mode=2:rate=27000000/900000)
[16:11:17] + frame rate: 23.976 fps -> peak rate limited to 30.000 fps
[16:11:17] + Output geometry
[16:11:17] + storage dimensions: 1280 x 528
[16:11:17] + pixel aspect ratio: 1 : 1
[16:11:17] + display dimensions: 1280 x 528
[16:11:17] + encoder: H.264 (libx264)
[16:11:17] + preset: fast
[16:11:17] + profile: main
[16:11:17] + level: 4.0
[16:11:17] + quality: 22.00 (RF)
[16:11:17] + color profile: 1-1-1
[16:11:17] + chroma location: left
[16:11:17] * audio track 1
[16:11:17] + name: Ita Ac3 5.1
[16:11:17] + decoder: italiano (AC3, 5.1 ch, 384 kbps) (track 1, id 0x1)
[16:11:17] + bitrate: 384 kbps, samplerate: 48000 Hz
[16:11:17] + mixdown: Stereo
[16:11:17] + encoder: AAC (libavcodec)
[16:11:17] + bitrate: 160 kbps, samplerate: 48000 Hz
[16:11:17] sync: expecting 299458 video frames
[16:11:17] encx264: min-keyint: 24, keyint: 240
[16:11:17] encx264: encoding at constant RF 22.000000
[16:11:17] encx264: unparsed options: level=4.0:ref=2:8x8dct=0:weightp=1:subme=6:vbv-bufsize=25000:vbv-maxrate=20000:rc-lookahead=30
x264 [info]: using SAR=1/1
x264 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 UnalignedStack
x264 [info]: profile Main, level 4.0, 4:2:0, 8-bit
[16:11:17] sync: first pts audio 0x1 is 0
[16:11:17] sync: first pts video is 450
[16:11:17] sync: "Capitolo 1" (1) at frame 1 time 450

Log after crash shutdown (not reboot):

HandBrake 1.7.3 (2024021000)
OS: Microsoft Windows NT 10.0.22631.0
CPU: 13th Gen Intel(R) Core(TM) i5-13400T
Ram: 7846 MB,
GPU Information:
Intel(R) UHD Graphics 730 - 31.0.101.3790
Screen: 1920x1080
Temp Dir: C:\Users\commerciale01\AppData\Local\Temp
Install Dir: C:\Program Files\HandBrake
Data Dir: C:\Users\commerciale01\AppData\Roaming\HandBrake

[17:05:43] Compile-time hardening features are enabled
Cannot load nvEncodeAPI64.dll
[17:05:43] vcn: not available on this system
[17:05:44] qsv: is available on this system