VIdeo card help :)

Hi, I’m looking to upgrade my video card on my Dell Dimension C521 as well basically because it sucks and I have just upgraded my ram to 4gb which i have just bought it is currently 1gb my pc specs are
vista 32 bit
amd athlon 64 x 2 dual core 3800 + 2.00gz

Basically I have a few games that don’t look that good on my PC in particular i have San Andreas on quite low settings ( I’m not wanting to upgrade to play the likes of crysis 2 or whatever, just have a better pc.

first of all I am quite noobish, as in device manager it says my display adaptor is NVIDIA GeForce 6150 LE but the slot for the video card is empty - why is this?

also i want to buy this http://www.dabs.com/products/gigabyte-ati-radeon-hd-4650-1gb-gddr2-pciexpress-dvi-oc-5BS3.html?utm_source=google&utm_medium=product search&utm_content=Q200 would this work/ be any good on my pc, or could anyone suggest other ideas.

Sorry for the poor grammar and spelling its late for me :(.

EDIT
just to say I don’t have a budget as i just want to upgrade this as i don’t have enough for a new pc. also any suggestions on other upgrades to my pc will be appreciated. OR you could just ignore the link and suggest something else for me. Also I am from the UK.

That’s a good card and can run San Andreas with ease. As for your other question about the Nvidia GeFroce 6150 and nothing being in the slot, those are your onboard graphics.