the prefetch files (*.pf) is not necesary because is a backup of the programs...
These files are not backup files, but files specially ordered on a disk in order to improve speed of loading prefeched applications in Windows (Windows Media Player, Internet Explorer and so on). There is absolutely no reason for you to delete them, since they will be recreated the next time you run your applications.
Never know what life is gonna throw at you. ZubTech
Indigorose, I think you should return the money to this very unpleasant and uninformed guy.
The APMS returns an error code 1024 when trying to delete those files. It is obvious that Windows do not allow you to mess with these files. Windows Explorer and Command Prompt must be using some other approach when deleting contents of this specific folder, most likely some specific Windows API call. There is no reason what-so-ever that APMS File.Delete action would fail on this one folder only. By the way, this could be a Lua issue as well.