CCleaner is one of the best privacy cleaning software and it can also remove flash cookies from your PC, but there are Flash Cookies which aren't removed by CCleaner.
Here is how to completely remove flash cookies from Windows XP, Vista and Windows 7.
For Windows XP users: Run CCleaner and add the following two folders to the Include List. For that go to Options – Include – Add Folder, and then navigate to:
C:\Documents and Settings\ User name\Application Data\Macromedia\Flash Player\#SharedObjects
C:\Documents and Settings\User name\Application Data\Macromedia\Flash Player\macromedia.com\support\flashplayer\sys
Now add the following file to the Exclude list. For that go to Option – Exclude – Add file and browse the following file.
C:\Documents and Settings\ User name\Application Data\Macromedia\Flash Player\macromedia.com\support\flashplayer\sys\settings.sol
For Windows 7 and Vista users: Add following two folders to Include list
C:\Users\User name\AppData\Roaming\Macromedia\Flash Player\#SharedObjects
C:\Users\User name\AppData\Roaming\Macromedia\Flash Player\macromedia.com\support\flashplayer\sys
In the Exclude list add the following file:
C:\Users\User name\AppData\Roaming\Macromedia\Flash Player\macromedia.com\support\flashplayer\sys\settings.sol
[Note: 'Please enable ‘Show hidden files and Folder Option before proceeding. For Windows XP go to Windows Explorer – Tools – Folder Options – View and enable ‘Show hidden files and Folder’ option. For Windows 7 & Vista got to Windows Explorer - Organize - Folder and Search option - View – and enable ‘Show hidden files, folder, or drivers’] - [Via]