Well this is my girlfriends computer, I haven't taken a look for myself yet, but when she turns her pc on, you know the button on the monitor, like theres orange for standby, and green for on, it goes orange, green, then back to orange after a second or two.
I had this a few months ago, and it was just the power cable come out a little bit.
She said it happened after they had a small power cut (they been having a few recently - lightning).
I know it's not advisable to keep it on in storms but she did.
Oh and it makes a screeching noise for a few secs when turned on, bit like a dial up dialling up, that kinda sound but not.
The system is pretty much one of these:
The psu is just generic i think, so could a surge of damaged the monitor / graphics card? Or what other errors can cause this.