Are you using the CCleaner registry cleaner?
Bleeping Computer DOES NOT recommend the use of registry cleaners/optimizers for several reasons:
Why you should not use Registry Cleaners and Optimization Tools
There are numerous programs which purport to improve system performance, make repairs and tune up a computer. Many of them include such features as a registry cleaner, registry optimizer, disk optimizer, etc. Some of these programs even incorporate optimization and registry cleaning features alongside anti-malware capabilities. These registry cleaners and optimizers claim to speed up your computer by finding and removing orphaned and corrupt registry entries that are responsible for slowing down system performance. There is no statistical evidence to back such claims. Advertisements to do so are borderline scams intended to goad users into using an unnecessary and potential dangerous product.
Credit for this goes to Quietman7, one of our Global Moderators.
Try doing a System Restore, use a restore point prior to making and changes including using CCleaner.
What is the make and model of this computer?
Do you have the installation disc for this version Windows 7?
Edited by dc3, 30 April 2016 - 10:59 AM.