Whats the biggest video card I can use in my pc?

I have an older desktop pc I still use occasionally and would like to upgrade the graphics card . I would like to be able to ply the sims 3 on it if possible and would like for it to have a svideo to tv output on it. It currently has xp pro, 1gb ram, and a second hard drive. The rest is factory spec. 80gb and 150gb hds if it matters. I would like to upgrade the ram in the future so if that is required I don't care to do so. It is a mpc client pro 345.

Also sorry for spelling issues I am posting from my mobile phone.

I think that would depend on the system requirements for Sims 3, your motherboard and power supply.

Oi. Its pretty much a relic.. You can only run pci and agp.
Here are you only choices.
Newegg.com - Computer Hardware, Video Cards & Video Devices, Desktop Graphics / Video Cards, AGP 4X/8X
and
Newegg.com - Computer Hardware, Video Cards & Video Devices, Desktop Graphics / Video Cards, PCI

Expensive upgrades for the system. But they all should work. I'd get the agp interface over pci