Friend of ours had that problem. He'd bought himself a 2-gig Toshiba with Win 7. Over the years, he'd installed heaven knows how many programs, including multiple anti-virus programs and more toolbars in his browser than he knew what to do with. And he kept on interrupting Win updates, choosing to leave the computer on overnight once a week. Of course, the machine became slower and slower with time until finally thing poor thing would nearly bog down completely with just a simple update operation. Train wreck. And he thought he needed a new computer.
So I uninstalled bunches of unneeded programs and tons of extensions. (He didn't know what most of them were.) Updated Windows. Explained to him that he should NOT turn off his computer during update installs. And got an extra 2 gigs of memory installed. The computer is now running like new.
:(
Lynn