From what I remember about the stuff in your computer,you have maybe two regular pci cards,1 hard drive maybe one extra systen fan,and your cpu.Sorry bout not getting back to you had to leave my house.Ill go check it myself.OK,heres the news.With a 7900gs youll need at least 420 watts from a good power supply,maybe forty watts less from a lesser graphics card.But believe meI had the same set-up mother board as well as radeon xpress 200 integrated graphics as you.I added a good 420 watt psu and added a huge graphics card(very high wattage)Tho you do have a few more things on your computer than me,I think a 420 to 450 watt psu should be your first step,thwen go with at least a 1600 ati or a 7600 nvidia card,may be a lil more than you want to spend but belive me when I say everything visual will get LOTS better John