Computer slow on one user account, not the other

When my husband opens I.E. on his user account, it can take 5 minutes or more just to load the intro page. It can also take a long time for other pages to open, but not as bad. I defrag the disc every couple of months, I've deleted his temp. internet files, history, and cookies, and it seems to make no difference whatsoever. On my user account, I.E only takes a minute or so to load the page. Any ideas as what would cause the discrepancy?

A faulty or problematic add-on. Reset IE. Open control panel -> internet options -> advanced -> RESET. Delete personal settings and data if given the option to in IE8. These instructions only work with IE7 or newer. Perform these instructions from your husband's account.

Ok, I've reset everything. Tonight I also deleted and reinstalled firefox, and ran chkdsk, because I got the same msn messenger corrupt file thing again. We'll see how everything does when he's on line tomorrow. Thanks!