You don't have to buy a "new" computer I'm new here, but I just built a custom AMD gaming desktop for $1275 exact (yes I'm a AMD fanboy) all you need is a motherboard and processor, along with some since your computer sounds like it's from the Stone Age. I would intel or AMD gets the job done, some argue Intel "iz teh best" but I got my motherboard for $105 and an AMD 8320 for $180 total that was $285 which is what it would cost for a decent intel CPU (some will argue power usage and costs) but to answer your question I would look on new egg for a motherboard and CPU and ram, total it should cost you $350-500, they have motherboard cpu combo's if your on a budget and ram is pretty cheap and depending on your Operating system you may not be able to handle more then 4-8gigs. If you need help just message me.