Video card compatible? First VC purchase.

I'm considering upgrading from onboard video to a video card. I haven't done this before, so any help would be appreciated.

[Edit: almost forgot - I'm not looking to run any new games. I'm just looking for something that'd be a significant improvement over onboard video and that'd run Vista fine if I ever decide to upgrade to it.]

First, here's the card I'm thinking of getting:
http://www.newegg.com/Product/Product.aspx...N82E16814500030

CPU: AMD Athlon™ 64 X2 4200+ dual-core processor with AMD64 Technology
http://support.gateway.com/s/PC/R/1009153/1009153sp2.shtml

Motherboard: FIC K2BC51 Motherboard with NVIDIA GeForce 6100 Chipset
http://www.fic.com.tw/product/motherboard/AMD/k2bc51lf.aspx
http://www.fic.com.tw/product/motherboard/...es/K2BC51G9.jpg

Case:
http://support.gateway.com/s/CASES/3502125/3502125sp3.shtml
http://support.gateway.com/s/CASES/WME1T49...493-001iv.shtml

PSU: 300 Watt Power Supply uATX/BTX Non-PFC
http://support.gateway.com/s/POWER/6506054...06054Rsp2.shtml

More: Gateway GT5228 Media Center Computer
http://support.gateway.com/s/PC/R/1009153/1009153nv.shtml

While researching this, through google, a few people have pointed out that the PSU should actually be good enough for a 7600GS.
http://www.tomshardware.com/forum/209966-33-7600-watt

"You should not need to upgrade your supply as it is actually has closer to 400 w of rated output plus an additional 200 w 12 v rail for your add on video card. I'm running an OC 7900 GS on the same machine and have no problems. Good luck. "
http://www.tomshardware.com/forum/209965-2...-gateway-gaming

Not to say I know that this is a good thing to do.

Anyway, I was just wondering if anyone would be able to tell me if this card wouldn't fit or some other potential problem.

Other concerns:

I've also read from a few people on other forums that this MOBO's PCI Express x16 went dead for them after about a year. I guess there's nothing I can do about that, unless a lack of power would cause that to happen.

Lastly, would this card also work in a new system which uses PCI Express 2.0 x16? (Just in case the 1-year death problem happens for me too.)

Thanks for any help.

I think it would be better to stick with a Nvidia upgrade. You should be able to just plug the new card in. It will at most require a driver update, instead of a removal of the old nvidia driver first, which can be tricky, followed by a ati driver install.
The 7600GS should be OK.