Weird Turn Off Issue

The other day when I put a new video card into my computer, I was plugging everything in and I hit the power supply switch and it turned my computer off. My computer has a button on the front that is supposed to do that, after you press it when the switch is on. I checked inside and the cords running from the power and reset button seem to be hooked up just fine. I checked the BIOS and power options which both said that the power button should be what turns it on. I don't have a clue what else I can do. I've been having so many weird things like this happening over the last couple days.

Windows XP Professional
Pentium 4 2.4Ghz
512mb RAM
Nvidia GeForce4 MX 440 (Temporary, upgrading to Radeon x1600 pro)

 

Can anyone help me figure out what to do? I'm still not able to turn off my computer (without hitting the power supply switch) and it's been like 3 days.