I have had a few problems with power supplies before. There is an easy way to check the wattage of your power supply, simply look at the sticker that is usually on the side of it, you may have to unscrew it from your case. If you want to check the fuses inside the power supply that will give you an idea if it was a blown fuse due to all the peripherals. Otherwise you can ask a friend if you can borrow his power supply just to see if that works. Power supplies are fairly cheap, 15-30 bucks for a 450w, which would probably be enough to run everything you have. Your problem sounds a lot like what mine was before though, so i can almost assure you that you didn't do anything wrong w/ the video card. good luck.
If it aint broke, fix it till it is.
MSI K8N Platinum
Athlon64 3500+ Skt. 939
Corsair TwinX 3200 1GB Dual Channel
2 80GB SATA 150 in Raid0
Sound Blaster Audigy Platinum
Sapphire ATI Radeon x850XT
Sony 48x12x48x16 CDRW/DVD Combo