You need to remove the cookies from your browser once in a week. You have to perform disk cleanup and defragmantaion to speed up your PC. Sometimes this problem occurs due to RAM. So you can increase the RAM.
Ccleaner does all that with out having to open a million windows.
Lots of good advice in these posts! You got good stuff.
I swear by a utility program (easy to get) called CCleaner (see pirform.com) which cleans all those nasty files very fast. It also fixes Registry errors (common problem with slow computers). My computer guy got it for me and I am extremely happy with it.