I was going to suggest buying a cheap video card to upgrade the integrated graphics (which would probably be enough to keep you going for a while) however it appears your motherboard does not have an AGP slot, and certainly doesn't have the newer PCIe slot. Upgrading RAM may be an option, but the beyond the 512mb already installed, the integrated graphics will still severely limit the performance.
Because of this I can only suggest buying a new(er) tower.
Good Luck