This is a warning message of your operating system for all local disks which have less than 200 MB free space. There are two options to avoid this message.
CmDongles can be configured to be detected as a local disk or removable disk. The low-space message usually appears only for CmDongles configured as local disks. You can reconfigure CmDongles as removable devices:

• Open a CodeMeter Command Prompt using
  "Start | All Programs | CodeMeter | Tools | CodeMeter Command Prompt".
• Read the current configuration.
  Execute the following command, replacing the <serial> with your CmDongle serial number, e.g. "1-123456":
  cmu32 -s <serial> --show-config-disk
• Reconfigure your CmDongle to be detected as removable device.
  Execute: cmu32 -s <serial> --set-config-disk RemovableDisk
• Remove and replug the CmDongle.

Please check whether everything works as expected. There have been cases in which a server did not boot correctly with plugged-in CmDongle configured as removable disks.

Alternatively, you can disable this message. Note, however, that you will then get no message, if your system drive runs out of space. To disable this message, please proceed as follows:

• Open the registry editor ([Windows Key] + [R] and type in regedit into the field).
• Navigate to the entry
  "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer"
• Add a new DWORD value (32-bit) NoLowDiskSpaceChecks"
• Set this value to "1".