Hey... nice boards ya got here

. Anyway, I'm not 'real' computer literate and I've been looking everywhere for an answer to this and cant seem to find one so I thought I'd ask you people (as it seems you guys/girls know your stuff).
I just bought a PNY GeForce Fx 5200 128mb PCI video card for my computer (I would have gotten an AGP, but I don't have a slot in my machine). I installed it and everything works good... except the card. I mean, don't get me wrong... it is slightly better than the onboard video but nothing great.
I don't do anything real high end with my machine... mainly gaming/photoshop and illustrator/and a 'little' 3D modeling. So with that in mind, I would have thought that this was a decent buy for my needs.
I've talked with a few people and they have all told me that this card should be able to do most of what I want no problems... but that isn't the case. For example I can't even run GTA Vice City in any other resolution other than 640X480 16bit color or else it starts getting pretty choppy (even in 640x480 it's not real great)... actually, scratch that... it gets really choppy.
Everyone I've told about this problem basicly says that the video card should be able to handle GTA at least and that I may have a prolem else where... but I'm lost as to what could be making my system perform so crummy (granted it's nothing top of the line).
Anyone have any experiance with these cards or does anyone have any tips to speed up the performance of it? Or diagnostic software to see what the deal is?
this is quite fustrating... I would have figured that the $$$ I dumped into this card (120.00) would have sped things up quite a bit, but it's not much better than my onboard video. BTW... my specs are:
eMachine (don't laugh

) T2240
Pentium Celeron 2.2GHz
640 Megs of DDR ram
onboard sound
the above mentioned card
40 GB WD h/d
yada yada yada..
oh.. and XP home edition
I ran spybot too, just to see if I had some spyware that was eating up resources and it came up clean... I'm lost, any suggestions or advice is highly appreciated. I can always take the card back... the other one I was looking at was a VisionTek Xtasy 9200 SE 128MB PCI (ATi). Not sure if that would do me better or not, the reviews I read on both cards made me want to go with the Nvidia card over the ATi...
reguards and thanks for looking,
-Steve