When running Pro Tools on Windows XP make sure that the program is not being run in Windows 2000 compatibility mode, otherwise this error may result. To turn this option off:Navigate to C:\Program Files\Digidesign\Pro ToolsRight click on the Pro Tools application and select PropertiesClick on the Compatibility tab and check the box for "Run this program in compatibility mode for:" and choose "Windows 2000" from the list of options.Click Apply, then OK.When this mode is then disabled, Pro Tools will ask for the key disks again and once reauthorized (without using an additional authorization count) everything will work fine. Re-enabling Win2000 compatibility will bring the 2108 errors back.