Updating my video card

I'm planning on getting a new video card for my PC (I currently have an NVIDIA GeForce 6100 nForce 405) so that I can actually play new games on my PC. This is primarily to allow me to play Dragon Age on PC, but I would also like to be able to play most other new games (specifically need to be able to play StarCraft II whenever the Hell it comes out), but it doesn't need to be totally top of the line or anything, just adequate, I'd really appreciate help and suggestions for what to get, please keep in mind I know next to nothing about computers so use small words my puny mind will be able to understand

Well, it is top of the line, but definitely worth it; the ATI Radeon 5870. This is your best bet, as it'll last you for a good while and then you can always Crossfire it, plus it's currently the only Graphics card that supports DirectX 11. (It's little brother the 5850 may also support DirectX 11).

How old is your PC? Because it's possible your motherboard doesn't have a PCI-E slot, which is the interface used by modern graphics cards. You current GPU is located on the motherboard and not on it's own separate board (if you open your PC case you'll actually see there is no graphics card). You have a decent CPU and enough ram so buying a new motherboard that supports the latest graphics cards is your best option, and it doesn't need to cost much. 
 
If you want to find out stuff about your PC, download a program like EVEREST. EVEREST will list your hardware specs and will tell you whether your motherboard has PCI-E slots, which is what you want.

There's no point in upgrading your GPU with that little bit of RAM, you're going to need at least 2GB more. As for your GPU it would help to know your power supply; if it's 300 or something which is what I'm presuming it's not going to be able to handle modern cards. 

" There's no point in upgrading your GPU with that little bit of RAM, you're going to need at least 2GB more. As for your GPU it would help to know your power supply; if it's 300 or something which is what I'm presuming it's not going to be able to handle modern cards.  "