[Retlaw]

Hi Margaret.

Sounds like dust iside the computer.

I get that problem every so often, my computers are under the desk,
every so often I take the covers off and blow the dust out,

take the cover off, if its an upright you will find a screw at the back, unfasten it and and side should slide off, inside on the mother board you should see a small fan ontop of the CPU, I'l bet the fan blades are mucky, hold the fan blades still with a pencil gently ,and use a small artists paint brush to clean the fan blades, make sure the air vents are clear on the power pack, and the vents on the casing, don't catch any connections but make sure they are all tightly in place. then put cover back and plug all the externals back and it should be OK.
Don't worry about having to change to vista you can always take the hard drive out and replace it with the one you are already using.
Retlaw.