go to C:\Program Files, delete the Hitman Pro 3.5 folder, if available.open the Start Menu, view All Programs and delete the Hitman Pro 3.5 folder (if available).Step 3 - Clean up possible remnant files and folders, by deleting the following: Step 1 - Make sure you write down your Hitman Pro license somewhere on paper, or make sure you have it saved on your pc in a. Looks like there is some problem with writing to the registry, try the following.