Well, I see two things that are really holding ya back.
- Windows Vista {32bit}
- Only 3GB of RAM {unless you have more, and aren't using it due to Vista being run in 32bit mode, you need to be running 64bit or all you have access to is 3.2gb of RAM}
Vista was never great for gaming, its eats up a ton of resources, putting a lot of stress on your PC overall, and it takes as much as 2gb of RAM to keep it running steady. Leaving you with only 1gb for your gaming and other applications. If you can afford Win7, or can get a copy from a friend or whatever means, do so...immediately! It runs amazing well, far better optimized for gaming.
I know someone will counter me on this, and say you really don't need more RAM than what you have, but in all honesty you do, especially if you want a smoother gaming experience. If ya don't know how RAM works, in the most basic form, its mainly just temporary data storage from your HDD, where your CPU and GPU pull data from. However if you don't have enough RAM to hold all the data you currently need then this is where a majority of slowdown and lag can spawn from.
Your RAM has to constantly keep communicating with your HDD, erasing data its not using expressly at that moment and swapping it with data that it needs. Then say you run into a new zone or another player with a set of armor that isn't loaded into your RAM...once again your RAM has to make room for this new data by swapping out stuff its not using for what it needs right away.
Anyway, what I'm getting at, the more RAM you have, the more temporary data you can have stored, immediately accessible by your CPU/GPU without the need to swap data constantly. Data stored in your RAM is also always there until you reset or turn your PC off.
{yeah sorry about the not-so-proper-technical ver....all those terms get jumbled around I forget them most times, but I know how it all works...LOL}
Anywho, as I said upgrade to Win7, and get yourself some more RAM...its super cheap right now and I bet that will help solve your problem, not completely, but by a great deal. I recommend you get 6-8gb of RAM...you can never have too much.