A Computer Question, concering gaming.?

Windows Vista is notorious for being buggy although it ran a lot faster than XP. If I were you, I would get Windows 7, legit or otherwise, because it's on the whole quicker. If you can't afford that, probably the most important hardware upgrade to make is just to get that extra 1GB of RAM to help clear the gap a little; 1GB really makes a difference in gaming. Don't waste money on a new processor or graphics card as if they're a few years old they'll be fine. RAM seems to wear down a fair bit over time in my experience so I'd reccommend upgrading.