NIST's Guide to Application Whitelisting

NIST have some great guides available (http://nist.gov), they have just published one on White listing, a very sensible security measure, worth a read, remember it's only a guide not hte bible so consider any changes you make to you environment before deploying them!
http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-167.pdf