Note: This review addresses v1.8.9 of the software.
If Windows won't let you manually delete a program file or folder, try Cedrick Collomb's free Unlocker. Once installed, Unlocker comes up automatically when Windows refuses to delete, move, or rename a file or folder, or you can launch it from the file or folder's context menu. Once up, it shows you what processes are hanging onto the culprit and lets you kill them.
Note: This link takes you to the vendor's site, where you can download the latest version of the software appropriate to your system. This program is donationware. It is free to try, but the author accepts and encourages donations towards further development.