Went to do a Disk Cleanup, had not done this for a month or so

Anyway when it came to deleting compress old files it shows 75,237KB when I went to view the files in that folder there were none there!! Re-Booted the computer then tried again, same result, the programme cleans up the files but still shows that there are 75,237KB in the folder yet nowt there.
Have 'Show Hiden Files' checked, cannot think what the problem might be, if they were deleted then why does Disk Cleanup show that they are still there?
Any help would be appreciated
Regards
Nigel.
I used to be an optimist but with age I am now a grumpy old pessimist.