Dec. 12, 2013 - Here's the Paint.Net fix! I could not install, uninstall or even use Paint.Net without getting the following message.
"Error: There is a problem with this Windows Installer package. A program required for this install to complete could not be run. Contact your support personnel or package vendor” when trying to uninstall Paint.net"
After trying to uninstall and reinstall Microsoft .NET Framework 3.5 SP 1, as suggested at one Microsoft site, I found the following link whichtotally resolved "ALL" my Paint.Net installation problems.
Microsoft Fix-It
http://support.microsoft.com/mats/Program\_Install\_and\_Uninstall
After using Microsoft Fix-It, the program states that this service is no longer available but thankfully it's still working at the time of this comment. Good Luck!