thanks, i just forced my computer to be a windows 7, btw, what is the lowest video card could i buy for my computer to have direct 3d acceleration?
It's better if you just get a new computer. Intel Pentium 4 is a really old processor, and most people have at least 4GB RAM installed - you don't even have 1GB. If you buy a 660 Ti, 7850 or something like that, you'll just bottleneck your system - the processor and RAM won't be able to cope with the graphics card, and you'll pretty much be paying $500 to use $30 or $40 of the card.
Even if you wanted to upgrade your computer, your motherboard may or may not support the RAM, socket for the CPU etc. In fact, I don't think your computer even has PCIe slots to put the cards in.