My screen flickers black for a split second, then everything stops responding. Audio cuts off, cursor won't move, ctrl-alt-del does nothing. At first this happened at random, usually within about ten minutes of startup. Got worse very quickly, and now I can't even load Windows before it happens. Can't even start in Safe Mode. Always seems to get through the BIOS fine, though.
Before this, I noticed my computer wouldn't recover from Sleep mode on the first attempt. Either I'd get a black screen, or the login screen would show up but keyboard and mouse wouldn't respond at all. LEDs on keyboard didn't work, no light from optical mouse. Switching off and on again would resume Windows as normal. Don't know if this is related.
When I first noticed the problem, I tried a system restore. No change. After Windows stopped loading altogether, I tried a clean boot. Same problem. Screen flickers, then freeze. Doesn't seem to happen at any particular point; sometimes it's when the Windows logo appears, sometimes when the progress bar is up, sometimes I get a black screen right after choosing to start windows. I also tried booting from a recovery disk, and again, same problem. Says it's loading the files, flicker, freeze.
I'm running Windows Vista Ultimate 32-bit, and I haven't made any recent system changes.
I'm guessing this is hardware related since I can't even boot from a CD. I managed to run Crystal Disk Info before Windows stopped loading, and it reported no hard drive problems. I also tried to run Windows Memory Diagnostics from the boot menu, but I'm pretty sure that froze as well. Stuck at 0%, and pressing Esc to exit did nothing.