It depends on performance.
If you want improved performnace, study/resolve errors in your Event Viewer>Admin View. Click through your WEI score link at Control Panel>System to use Advanced tools to view Performance-Diagnostics log and Generate a System Health report.
Edit msconfig>Startup to remove all but AV and any programs which absolutely must start up with computer - all others are freeloaders on your RAM and CPU. I startup only AV and MS>Gadgets+StikyNotes.
Test your HD by running full CD diag/repair scan: Hard Drive Diagnostics Tools and Utilities (Storage) - TACKtech Corp.
followed by chkdsk.
Next run memtest86 CD overnight to stress test memory: Memtest86 - Download Page
System file checker was a good choice. I use it as a last resort before Repair Install
- which keeps all of your programs, files and settings in place but reinstalls the OS. It can fix many problems.
It is doubtful that CCleaner messed up anything as I have used it for 10 years and never heard of it causing problems. More likely unnneeded tweaking or settings corruption which might
be resolved by Repair install but could be reimported as a setting.
When you get it running as you like, then save a Windows 7 Backup Image externally (or to a primary partition) so you never need to reinstall again - just reimage the HD or a replacement from image using DVD/Repair CD. This might be an incentive to do a Clean Reinstall in the long run.