Try doing a disk clean up and defragging.
This tends to happen after a while because you usually end up with a lot of programs installed on your computer. Windows tries to make all the little icons show the correct thing which also takes a bunch of time. The only thing that I can think of to fix this is uninstall the crap that you don't use anymore.
If you have antivirus software, that could also slow things down depending on the settings you have (you mentioning Outlook makes me thing this is a likely cause because anti-virus programs love scanning the shit out of your e-mail).