Can't find external references
To reset the registry follow below:
Exit out of SolidWorks. Go to start and type in regedit (if you're using win xp you can use "run") and double click on regedit
Go into the hkey current user folder and then into the software folder
Rename the solidworks folder to something else like solidworksold; this way if the issue is not a corrupted registry key, you can revert back to your old settings. Then open solidworks and test the issue.