CCleaner does not clean Media Player Classic history.
For example, the contents of the registry before and after CCleaner:
[HKEY_CURRENT_USER\Software\Gabest\Media Player Classic\Settings]
"File Name 0"="D:\\Video\\film.avi"
"File Position 0"="18187232"
[Media Player Classic]
ID=2084
LangSecRef=3023
Detect=HKCU\Software\Gabest\Media Player Classic
Default=True
RegKey1=HKCU\Software\Gabest\Media Player Classic\Recent File List
RegKey2=HKCU\Software\Gabest\Media Player Classic\Recent Dub List
RegKey3=HKCU\Software\Gabest\Media Player Classic\Capture|FileName
FileKey1=%appdata%\Media Player Classic|default.mpcpl
is what is currently in CCleaner. Try adding the following to winapp2.ini
[Media Player Classic More*]
LangSecRef=3023
Detect=HKCU\Software\Gabest\Media Player Classic
Default=False
RegKey1=HKCU\Software\Gabest\Media Player Classic\Settings|File Name 0
RegKey2=HKCU\Software\Gabest\Media Player Classic\Settings|File Position 0
Are there any numbers beyond 0?
If by chance you've ever enabled MPC's option to save settings to .INI file instead of using the registry then CCleaner won't be able to clean it, if for some reason it's stuck in that .INI file mode only.