New
#11
The eraser tool will literally take care of "everything" on the drive as well as using the DiskPart command "clean all" while booted live from a 7 dvd. But that would be taking things a bit too far especially if you lack any recovery disk. The quick way however requires a live disk just the same to see the C primary not the recovery partition removed for a new one to be created and formatted for use.
On previous builds when simply repairing things rather then a clean install on a new primary things never did go so well. Once you have a fresh primary and good clean install on you will want to create a good image of the drive for safe keeping unless you discover the drive is having problems of it's own.