Diskeeper 10
http://www.diskeeper.com
Doesn't really protect your computer against anything other then greatly increasing system performance, and it is far more efficient then the standard Windows Defragmentation software included in Windows.
It can defrag parts of the hard drive that the standard one can't (Like your Master File Table and Paging file, it can do this by defraging it during the boot up process), it can expand you Master File Table to include more entries which prefents file fragmentation. It can move all Folders to the beginning of a drive which increases disk read time, and two of my favorite features: 1) You can defrag multiple drives at once, and 2) The programs smart, It pauses the defragmentation process if you're using the drive, so you can use the computer while its defragmenting (When the feature is activated in the options)!
There is a 15 day trial version for Download on their site.
Home Edition is about 30 bucks, but I recommend the Professional Edition which is closer to 50 bucks.