Computer choking.

I am completely stumped as to why this happens.

On random occasions, my OS will cease to respond.
A few seconds later, the mouse freezes.
A few seconds later, the screen goes black.
Then there's a 20% chance the monitor throws itself into power saving and never gets out.  Otherwise, everything returns to normal a few seconds later.

I scanned the computer.  No viruses, no malware of any sort, and the HD is in fine condition.  Nothing was installed/modified/uninstalled recently.  My component temps are all within the norms and I blew out the dust just a month ago.  As far as I've seen, there is no clue as to why that sort of problem would happen.

What the hell is going on?  What else can I check?

Reinstall Windows. Use the latest drivers after the reinstallation.

Check components for overheating

OP here.

>My component temps are all within the norms and I blew out the dust just a month ago.

Also, I managed to pin down the problem: whenever it happens, it is when Firefox is running.

I have this very exact problem. In my case, I think its a hardware problem related to my video card. The aforementioned symptons occur whenever I try to run HD movies or a game. I reinstalled drivers and updated everything and still the same. I checked the connections and everything was fine.

My card is kinda old so I was thinking about changing it anyway. What does /comp/ think of the nvidia 8600 GT/GTS 256MB? Decent enough to run TF2 or CIV4?