Which part to upgrade to run 25 mans?

[Merchy3]

Heya guys,

I was wondering which part I could upgrade and be able to run 25 mans. At the moment, I can't do jack in them for the laggs/freezes at times. I run 10 mans and 10 man heroics fine, (2/14 heroic atm), but want my options open so I might can run 25 mans on an alt with a friends guild or even raid finder for that matter. I purchased my computer from Wal-Mart prebuilt in later 2009 for $700 before I knew you could build a beast computer for that, it was the best they had at the time. I've upgraded my graphics card around the same time but the graphics card is the only part I touched and I'm on a hardcore budget atm and can't upgrade much or build a new one just yet, gotta make due with what I have.

Any info would be great and i'd appreciate it a lot, thanks.

OS - Windows Vista
Processor - Intel(R) Pentium(R) Dual CPU E2220 @ 2.40GHz (2 CPUs), ~2.4GHz
Memory - 5118 MB RAM
DirectX Version - DirectX 11
Graphic Card - ATI Radeon HD 5700 Series

[Merchy3]

Okay, thanks a lot for the fast response! I didn't think there was much wiggle room with it being that old and plus prebuilt from wal-mart. I think i'll just hold off and build me a decent pc in a few months or something, start buying a a few parts here and there. Thanks again.