Hi Muggyl,
Thanks for visiting Apple Support Communities.
If you are receiving errors in Windows after updating iTunes, I recommend completely removing and reinstalling the software using the instructions in this article:
Removing and reinstalling iTunes and other software components for Windows Vista, Windows 7, or Windows 8
http://support.apple.com/kb/HT1923
When reinstalling iTunes (step 3), be sure that you are logged in to your computer as an Administrator:
Make sure you have an administrator account.
To install iTunes or QuickTime, you need to log in as an administrator on the computer. If you're not sure you have an administrator account, you may find this Microsoft article helpful: Windows 7: How do I log on as an administrator? You can refer to the Help documentation from Microsoft, contact your IT department, or visit support.microsoft.com for more information.
From:
Issues installing iTunes or QuickTime for Windows
http://support.apple.com/kb/HT1926
Best Regards,
Jeremy