Outlook runs very slow and keeps crashing

Do you use Forms or Advanced features at all?

This site has information that will generally solve most issues:
http://labnol.blogspot.com/2007/03/microsoft-outlook-2007-running-slow-fix.html

Try those, and let us know. If you use Form functionality. You may need to clear your form cache. This can be done by deleting certian files.

This site will show you how to clear your cache, as well a saved view information (Your customized view settings) so you can decide what you would like to keep and what has to go:

http://www.slipstick.com/outlook/ol2007/slow.htm

Good Luck