This link takes you to an Infoworld discussion about encrypting your pagefile;
Infoworld
Here is how to do it in Vista;
Vista: Encrypt the Pagefile I would imagine it is done the same way in Windows 7.
Windows club has a 'Tweak" program that will make the setting change for you at
WindowsClub. PC World recommends this program.
Depending on your system, you may not notice the impact of encrypting the pagefile to its performance. It would not be necessary to delete it during each shutdown if it is encrypted, and that in itself is a huge performance gain.