If you are one of those guys who either want to keep the data on your harddrives secured from foreigners or you are just keen on the latest software technology you should check out TrueCrypt. TrueCrypt lets you encrypt files later to be mounted as a virtual drive. Imagine you want to share an important pile of data with your friends, with TrueCrypt done right you don't need to worry about its security anymore.
But there's more, you can of course encrypt an entire partition on your internal and external hard drive or USB flash drive. The encryption however is automatic, real-time (on-the-fly) and transparent too.
The new version 4.3 is now completely digitally signed by Microsoft and therefore compatible to Windows Vista and it's User Account Control System (UAC). So there is no hassle anymore if you want to fiddle around with it using Bill's latest creation.