[Unable to move beyond V5.45.6611]

Further, I am using Windows 7.

[Unable to move beyond V5.45.6611]

I recently renewed my subscription after it had lapsed for a short period.

I registered and went through the procedure to register.

I am having trouble updating to the latest version (5.51.6939) because I think the program is trying to install into 

Windows XP. Seems strange but I have removed every file relating to CCleaner except one file with prefix 5.51

I hope I have not confused you. Can you please help?