Ever since I got Windows 8.1 preview, Portal 2 seems to crash after 5 seconds when I launch it. I could launch it fine when I had Windows 8! Has anyone got it to work on Windows 8.1? If so how?
1I've removed the last question about downgrading from the preview as it's not on-topic for this site, but according to windows.microsoft.com/en-us/windows-8/preview-faq - "Uninstalling the preview isn't supported. However, it may be possible to restore your entire system to its factory condition."– Private PansyJul 16, 2013 at 0:34
Various answers here and here indicate that uninstalling and reinstalling the game will fix the problem (none of them mentioned if they tried verifying the game cache first, which should theoretically do the same thing, but be much faster).
This post also suggests that you may need special graphics-card drivers for Windows 8.1, which you should be able to obtain through Windows Update, or (failing that) from the manufacturer's website.
2I can confirm through testing with the final release of Windows 8.1 that this issue still occurs if you've upgraded from a previous version of Windows 8. Windows 8.1 automatically upgraded the graphics drivers as part of the upgrade process, verifying the game cache did resolve the problem without a reinstall.– kalinaOct 20, 2013 at 21:55