Can this prebuilt be upgraded?

Djiem

Hello all.
I have this computer here: HP a1540n

I've upgraded its video card in the past to play games (I've got an ATI Radeon X1600 512mb), and now that I have a 20" widescreen and Age of Conan, I think it's time to upgrade it some more.

Obviously, the first step is to install a new video card, which is what I'm going to do today, but I was wondering if it's possible to change the processor for a stronger one at all. If it is, is it simple? Do I have to worry about compatibility issues?
Or would I need to change the entire mobo (in which case I'd be better off just buying a new PC)?
I'd really like it if I could postpone the purchase of an entire machine until after Fallout 3 comes out (so that I get what's best then).
Thanks in advance.

EDIT: A friend of mine looked at the specs and told me it'd be possible as long as I get a processor with a 939 socket. What's your thoughts? Can I upgrade it for cheap, if at all? And if I can, what do you reccomend?

Bionic Monkey

Uh, a quick search on Newegg seems to show 939's are dying out, and the only available 939 CPU is actually weaker than what you currently have in there.

If you don't want to replace the mobo yet, I think throwing some more RAM in there is your only option for upgrade at this point.

Rook

I'd honestly just concentrate on getting a decent graphics card in there. You'll see a massive improvement if you stick an 8800GT in there.

Djiem

Yeah, just went out and got the videocard. Thanks for the replies.
I did a little search myself and couldn't find any stronger 939 chips, which is why I asked here.

I guess I'll just hold out until October then buy a new PC then.