Hi ralphwh, welcome to the forums
It could be that 1 or more of your system files may have changed (for the worse). You could try restoring your system files to their original state
1, open Command Prompt (start->All programs->Accessories) by right clicking and selecting 'run as administrator'.
2, type in
sfc /scannow
Once complete you may need to restart your machine
Hope this helps
OS