I want to play Counter-Strike and need a new video card.

Specs: (from General Panel of System Properties)

Windows XP Home Edition Version 2002 Service Pack 2
Dell OPTIPLEX GX270 Intel(R)
Pentium(R) 4 CPU 2.40GHz
2.39GHz, 768 MB of RAM

My current video card is a nVidia Geforce4 MX 420 in PCI bus 1.
I want to know if I have AGP slots or (even though this is probably impossible), PCI-E slots. What video cards are compatible that will allow me to play Counter-Strike. I already play Guild Wars, and it will run smoothly providing that I put the settings at their lowest. Any suggestions?

According to DELL you have a small or low profile desktop case which means you have to get a low profile graphics card.

Good news, it does appear that your model does have both PCI and an AGP graphics slot.

The trick is finding a decent graphics card in a low profile form factor, since most manufacturers only released entry level cards in a small form factor.

I did a quick search over at NewEgg and came across quite a few AGP cards, however, only a few are low profile so I suggest using this as a guide to noting all the low profile cards and what GPU make/model they use and compare that to Counter-Strike and what they recommend as the minimum graphics card supported

Thank you so much.