after all the good comments I have read in here about truecrypt I can't believe that It won't even let me simply encrypt a Partition.
Maybe you should try the Truecrypt Forum for faster Truecrypt support! http://forums.truecrypt.org/ Edit: OH! I see you are already a member over their!
arran, In place encryption for Truecrypt partitions is only supported for Windows Vista. System encryption is fine with XP, it doesn't touch your data, but with XP and second partition encryption you must start with an empty partition.