error opening file for writing

I have tried updating CCleaner but repeatedly get this error:

Error Opening File for Writing

C:/Program Files/CCleaner/CCleaner.exe

Click Abort to stop

Retry or Ignore

I have tried deleting the program and loading the latest version 1.23.160, I have tried turning off my firewall as well as using different file locations other than FileHippo. When I click Ignore, CCleaner version 1.22.142 is successfully installed.

This is the first time I have gotten this error message despite being able to update in the past. I am using XP SP2 on a AMD Duron with 479 RAM.

Any ideas???????????