Need computer advice on GFX card and some other issues.

Here are my current specs:
Intel Celeron 2.8GHZ single core i845G Chipset
1GB DDR Memory ( 2X 512 DDR pc2700 sticks)
 Nvidia GeForce 5500FX (PCI)
 Microsoft Windows XP SP3

 
I understand it is a very outdated system but what are my options for upgrades? I do NOT have a PCI-E slot and am not sure how much RAM I can put into the motherboard. I would assume it can handle at least 2GB, but I don't understand DDR vs DDR2 vs DDR3. It only has 2 memory slots, and I would like to stick 2, 2GB and try and get 4GB into it. The reasoning behind that is that I eventually want to build a new PC from scratch this summer, so spending money on some really good memory is fine with me, I'll just reuse the memory on my new PC (if applicable). 
 
I currently have 2 free PCI slots assuming I take the old card out. Basically what I am looking for is just something to run WoW and Star Wars Old Republic at a smooth rate. I don't need to play it on the highest res with the highest settings, but the reason why I stopped playing was because I just got tired of raiding with 10 FPS.
 
What are my options? keep in mind that I am working on a budget, I'd like to keep the total project under 200-250$.
 
I have a pretty good knowledge of computers and understand most things, but GPU's and memory confuse the hell out of me. Too many options to know what is best and what it all means for me.
 
Any advice would be GREATLY appreciated! Thanks in advance bombers.
 
Also, <>

No PCI-E slot = fail 
 
Buy a new machine. 
 
Sorry for not being more helpful, but I'm a bit busy at the moment. But yeah, new machine.  :P

No PCI-E slot = fail  
Buy a new machine.  
Sorry for not being more helpful, but I'm a bit busy at the moment. But yeah, new machine.  :P

I dont wont to discourage you, but a new computer is definitely a good idea.  Go to Microcenter.com or do some browsing and you can get a capable computer for around $300-$400.

That's very ancient, I'm sorry, however you have to buy a new rig for pc gaming. It's only a single core and that gpu is so weak, it won't play anything. Your upgraded options are limited because they might not sell such ancient parts, even if you can find them, it's not even worth it. I'm sorry how there are absolutely no other options right now, you can build a $500 rig and it would be better than what you have now, don't put money towards such ancient technology. You need at least a pci express to do anything meaningful in terms of pc gaming at the very least and a dual core processor.

Keep in mind that you've hit that curve where whatever you upgrade in this machine is not going to transfer over to the new machine, except harddrive, power supple, and optical drives.
 
Some quick searches show that your chipset only supports up to 2GB of RAM, and seeing as you only have PCI means it's going to be near impossible to upgrade the video to anything decent, if they even make anything anymore that beats the 5500FX.
 
Your best bet is to wait.

Not to sound like a dick, but like everyone else has basically said; you're fucked. There's absolutely no point in putting anymore money into your machine unless it's a brand new rig. Any money you DO spend on your machine trying to eek out any last upgrades and performance are going to be so marginal that you're pretty much throwing your money into the bin. Just wait and upgrade altogether when you can afford it.