What version of Windows are you running?
Andavari: Maybe.
If you are using Windows XP or Windows 2000, then download
Dial-a-fix-medium , double click it, extract it to a folder, double click on Dial-a-fix.exe inside of that folder, click on the Tools button (the hammer) then double click on Repair permissions. If you are using Windows 98 or Millennium edition, don't do any of that.
For XP/2000:
Click Start, Run, and then type/paste each of the following lines, one by one, including the quotation marks:
regsvr32 "%ProgramFiles%\CCleaner\CCHelper.ocx"
regsvr32 "%ProgramFiles%\CCleaner\CCListBar.ocx"
regsvr32 "%ProgramFiles%\CCleaner\CCListView.ocx"
regsvr32 "%ProgramFiles%\CCleaner\CCTab.ocx"
regsvr32 "%ProgramFiles%\CCleaner\CCTreeView.ocx"
regsvr32 "%ProgramFiles%\CCleaner\CCSubTimer.dll"
regsvr32 "%ProgramFiles%\CCleaner\CCSystem.dll"
For Windows 98/Me, replace %ProgramFiles% with C:\Program Files\ so each line would become:
regsvr32 "C:\Program Files\CCleaner\CCHelper.ocx" (etc)