Computer Problem -Help!

[Kapn_Kiwi]

Hey guys, my computer died on me last night. :
Not sure quite what's wrong with it. I left for uni in the morning, turning it off as I went out the door, and when I got home, it wouldn't turn on properly. The LED on the mobo's on, and when I turn on the PC, the fans all spin up.

However, after this, nothing much happens. My screen doesn't flicker to life, just sits there on standby (I've tried turning it off and on, and it still doesn't display an image), the mouse doesn't light up, and one of the lock-key status lights on my keyboard turns on, as usual, but hitting them doesn't actually change them. I've checked all the wires from the PSU, they're all in tight, I've tried unplugging my fans, case lights, and all drives bar my system drive, still nothing. I tried removing and reseating the RAM. I haven't checked to see if my internal speaker's plugged in yet, because I'd have to find the damn thing (not sure if I even have one) so I'm not sure if it's giving me beep codes yet.

Any ideas? It's driving me nuts.