If you are a gamer, and using simple terms, the 6600 GT is a much more powerful card for gaming over the plain 6600 card.  Both will work.  The plain 6600 will of course cost less, and is a good over all card, but won't give you as much game eye candy turned on.  Also more system ram will help as well.

Dim 4400 ( 3 Years 4 Months, going strong )
2.6 Ghz 400 FSB
1 Gb 2100 DDR Memory
20 Gb hard drive 7,200
Windows XP Home - SP-2
Leadtek 6600 GT ( AGP ) video
48xCDRW
17 LCD ( 1703 FP )
250 watt power supply

Yes, there is a long shot difference.

Thanks for the reply.

Yes it would be for gaming BF2 maybe.

But, is the GF6600 much better than the integrated Intel graphics media accelerator 900 the CPU came with? The reason I ask, is with all the talk about conflicts and adding new cards if the performance is not much better, I may just skip it.

Thanks again for your help.

Peace

Integrated video is ab out like a video card from 1998. A Geforce 6600GT is slightly more powerful than a high end $500 video card from 2003. There's a HUUUUUGE difference.

(And do get at least a 6600GT or 6800-they're a big step up over a 6600, and will last you a lot longer.)