linney's comments above where intended to make your resolve some "known" issues:
. clear your Temp folders.
. clear your System Restore older restore points
. clear up all sorts of regular junk
This is excellent advice, as the behavior of your system is not the normal one.
Double-click My Computer, double-click each of your drives one-by-one and select the Disk Cleanup tool. Select the 'Other Options' tab and cleanup everything that looks reasonable. Then the General Tab and start the cleanup.
If you have an issue with System Restore, the Disk Cleanup tool should resolve it.
Do not confuse System Restore with forcing a "System File Check" status check of your system EXE and DLL files. Start, Run, sfc /Scannow
will start the System File Checker. It takes a while, and says nothing while working. (Event Viewer will show you any complaints afterwards).
Reboot after each of the above operations.