My monitor doesn't want to stay on...

I've left the PC hanging in BIOS for now (& no problems with the monitor - so I know it's not that, nor anything too basic like the video card connection or VGA cable) but following my last reboot I can no longer login to Windows (single account, so it automatically logs in) without the monitor turning on & off at apx. 5 second intervals several times before it finally just goes black & stays that way.

I've also noticed that the cursor (which seems to be the only thing I can actively control - I can highlight the X to close Windows Live Messenger, but it won't respond if I click it) gets corrupted from time to time with some red & yellow pixels.

It's a fairly fresh build (last weekend) with an even fresher installation of Windows that I finally got updated & ready to play games last night... =|

I'm assuming it doesn't make any difference, but I had plugged in my joystick the time before I rebooted finally ready to really play a game... >_<

It's a legal copy of Windows XP Home (a 2002 Upgrade edition that was updated through all modern SP2 updates + WMP11 & ASP.NET 2.0) that has been used once before on a previous PC & it hasn't given me any problems over the past week. The last thing I did was use DC++ to transfer my Steam installation files from my old PC to the new one. XP Home isn't network friendly, so I couldn't do it through explorer...

I have absolutely no idea why this is happening, to be honest. I'm not running any anti-virus yet.

I don't know what the hell it was, but when I got home it had fixed itself. It was like it never happened...?_?...

Oh, and don't worry about the Steam part. I've done it before many times. I download the program from the site, install Half-Life & Half-Life 2 for all the base files on both engines, then I transfer over all extra files from my other HDD; or in this case my other PC.

I'll definitely make a note of the XP repair thing for any time I have a problem that doesn't go away. And I'll get my anti-virus on here as soon as I'm finished typing. That was scary.

Holy ****ing ****, it's doing it DURING THE WINDOWS INSTALLATION!?! O_O

...

It seems to have settled down now that I've reached some sort of window, but the resolution seems to be wrong & I can only see a corner... of... *goes to see what happens & finishes post later*

Well the resolution is still messed up, but the monitor has stopped flickering for now...?_?...

I'm frichen confused. This is beyond weird. Maybe I should have scanned with AVG after I installed it... >_<