You may have blown the BIOS somehow. I fixed one by removing the battery (clearing the CMOS). Let us know.

: First I'll tell you a little about my computer and then what happened. I'm running Windows 98 on a 1.4 ghz athlon processor on an ASUS A7M266 motherboard with 256 ddr ram; geforce 2 pro 32 meg ddr, 40 gig 7200 hard drive, 16, xgamer 5.1 sound card... I think that's all the important stuff that might matter. I've had the computer for 3 months and it's been working fine..until the other day. I was playing an online computer game (counter-strike) and the screen froze..not much of a problem. I tried to escape out of it...no luck, then I tried control, alt, del. out of it...no luck, then I just powered off the computer by holding the power button. When I turned the computer back on, the computer seems like it comes on, all the lights and fans turn on and it makes the sounds but the monitor will not come on. All the connections are good and i've checked the boards, nothing looks burned up. I even checked the monitor using a friends laptop and it comes right on. I thought my video card might be faulty so I went and bought a new one and still no luck. I know a little about computers (i put mine together) but this has myself and everyone I've asked so far completely baffled. If anyone has any ideas...they would be greaty appreciated, I NEED my computer back. Thanks