Does anyone know why my video has gone all pixelated white and black? All the footage seems corrupted but the files are ok.

You need to provide details for anyone to help

What kind of video are you editing?
Standard    720   x 480    DVD Resolution
720p        1,280 x 720    High Definition
1080p        1,920 x 1,080    Full High Definition
4k        3,840 x 2,160    Ultra-High Definition
8k        7,680 x 4,320    New, not widely used
-hint 4k/8k video on an underpowered computer will not play well

NTSC = 720x480 with PAR .9 to display at 4:3 or PAR = 1.212 for 16:9
PAL = 720x576 (I don't do PAL, so don't know PAR settings)
Exactly what is INSIDE the video you are editing?
Report back with the codec details of your file, use the program below
Free program to get file information for PC/Mac http://mediaarea.net/en/MediaInfo/Download
- a MediaInfo tutorial https://youtu.be/Ivy9ckSX1M0
- when you analyze your file in MediaInfo and post a screen shot in the forum, do so in TREE view
- post your information IN your message, not as an attachment that someone would have to download
Do not count on Windows to be fully up to date when it comes to device drivers
Go to the vendor site to be sure you have an updated driver for your graphic adapter
There have also been reports in the past that the latest driver is not the best driver
.
Also check (copied link) https://www.tomshardware.com/reviews/gpu-hierarchy,4388.html
Puget page has desktop and laptop computers... expensive, but at least some good ideas
https://www.pugetsystems.com/solutions/video-editing-workstations/adobe-premiere-pro/hardware-recommendations/
.
https://helpx.adobe.com/premiere-pro/kb/gpu-and-gpu-driver-requirements-for-premiere-pro.html
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nVidia Driver Downloads https://www.nvidia.com/Download/index.aspx?lang=en-us
-for all Adobe programs use the STUDIO driver, not the GAMING driver
-To achieve the highest level of reliability, Studio Drivers undergo extensive
-testing against multi-app creator workflows and multiple revisions of the top
-creative applications from Adobe to Autodesk and beyond
.
If you have a laptop you MAY also need to check for a laptop specific nVidia driver
-SOME laptops require an approved driver from the laptop company, not nVidia
.
AMD/ATI Driver https://www.amd.com/en/support
.
Intel https://downloadcenter.intel.com/product/211969/Intel-HD-Graphics-Family
https://www.askwoody.com/newsletter/free-edition-working-with-the-intel-driver-support-assistant/