I think "Bcastner" mention of giving your general Administrative user a password too would be worth a try.
The mention I made of Tweakui was just an rough guess I would not concern yourself too much with that suggestion if you are not a "Tweaker".
Registry Cleaner programs come in all sorts of packages, such as Norton etc. Some links.
jv16 PowerTools 1.4 released but not freeware (or RegSupreme)
Freeware. RegSeeker.
For future reference so you retain updates. Do you updates manually.
By following these instructions you can save any update to disk for later installation or reinstallation.
Perform the following steps to view the Windows Update Catalog:
Visit the Windows Update Web site:
Allow it to Scan for Updates and note the details of any updates offered.
Return to the home page of the Windows Update Web Site.
Click Personalize Windows Update.
Select the Display the link to the Windows Update Catalog under See Also check box.
Click Save Settings.
A Windows Update Catalog link appears under See Also. Click the Windows Update Catalog link.
Click Find updates for Microsoft Windows operating systems.
Click the appropriate product (windows XP SP1 etc.), and then click Search.
Click Recommended or Critical Updates.
Locate the updates you want, and then click Add.
Click Go to download basket.
In the Type or browse to the download location of your choice box, type the full path for the folder in which you want to save the patch. Or, click Browse to browse to the folder.
Click Download Now.