You can try using the System File Checker, by launching a elevated command prompt and typing
sfc /scannow
you might also consider a system restore point prior to the problem having manifested itself.
You can try some tender loving care
StartOrb->All Programs->Accessories->System Tools_>Disk Cleanup
and
StartOrb->All Programs->Accessories->System Tools_>Disk Defragmenter
But usually these types of issues are a result of third party programs, so....
have you installed, added, updated or tweaked any third party Explorer or Desktop addons, tweakers, shell overlays and the like.
Try safemode and see if the behavior is the same
Try a different user account (or create a new user) to see if the problem is unique to your profile.
Good luck, and...