A colleague of mine recently recommended this funky tool (http://www.piriform.com/CCLEANER) which has done a fantastic job of cleaning up my machine...
I've always wanted to know how to do this myself, so just thought I'd let you know if you were wondering as well. When searching emails you can use the OR operator as follows for quick search for people messages are from for example like this
FROM: (james OR robert)
This will find all emails that were sent from either James or Robert for example.