I am very sorry for not being specific. :(
I usually do it to clean the mostly the outside or casing of the computer. I simply use cotton cloth wet with dishwashing liquid carefully wiping the surface. I also use same procedure in cleaning computer tables. ;)
sounds like power supply problem to me.
try isolating you the power supply. you will also have to see if there is no bloated capacitors in the motherboard and graphic card.
I like to screensaver when I was young... like 10 years old, but now that I am working, screensaver has become unnecessary because my computer are too busy already hehehe...