Good evening brothers,. I am in need of desperate help : Summary : I have a 2004 desktop pc with specs : g*F*rce 5300pcx , 1GB ram, 500GB HDD , GA 8I915G-Duo motherboard and a cheap 350W supply. Original OS is on ( windows XP pro ) and running smoothly and fast . PC is virus free All is well . Then i change fans and supply to a 500W one. I get the PC back from the store and boot takes about 15min leading only to a desktop with 5 minute response time for the cursor to move ( 2 hours to open firefox) . After that i formatted many times and even changed the HDD , but the only OS that work properly are windows 7 and Ubuntu . Any XP or server 2003 version of windows ive tried ( and ive installed well over 100 different ones some even genuine) have the same lagging problem, they run really slow. Slipstreaming all the drivers didnt help . What can be at fault? keep in mind that windows 7 ran way too fast (so did linux) . Ram looked fine on task manager .