I'm having a recurring problem that's vexing me. For about a month I've had lockups where the computer monitor will blink off and go to random diagonal lines or blank. Sometimes it appears that it's in sleep mode but won't come out, and when you turn off the monitor and turn it back on, the monitor shows a test pattern - no signal. Sometimes the monitor blinks off then comes back on to the same screen but is unresponsive.

Another symptom - programs occasionally freak out: windows blink, other poltergeist stuff.

When it freezes, it becomes completely unresponsive and requires a hard reboot. When it comes back up it sometimes works ok for a while and then dies again, or it may be very slow and erratic on reboot, or it may freeze up again when Windows boots.

No viruses or spam to speak of.

I'm thinking:
1. CPU too hot (have installed new fan with no change, blown the dust out, but I think it could be damaged by heat)
2. bad video card
3. bad or overworked power supply
4. sound card bad

setup:
Windows XP Pro
ECS K7VTA3 motherboard
Athlon xp 2400+
BFG nvidia fx 5600
1 Gb RAM
430w power supply
2 optical drives
3 hard drives
audigy soundcard
NIC card
firewire card
2 case fans

I haven't changed any video drivers. The soundcard is the newest component which I installed in December.

Is this thing fried?