Hi
There is a big difference between Repair a Windows installation and Restore a Windows Installation
Retore usually wipes out every thing on C: drive so you do not do this if you have important data on C:
Repair requires a USB memory stick or CD/DVD System Repair disk built from same version of Windows 7 on your problem PC
eg x86 = 32bit or 64bit versions and Win 7 or Win 7 with service pack 1
(don't worry about Home, Professional or Ultimate, OEM or retail)
see Microsoft site for details
http://windows.microsoft.com/en-AU/windows7/Create-a-system-repair-disc
for Recovery see 'user guide' or FAQ on Manufacturers web site for detailed instructions
regards
Mike Barnes