Why won't TechTool Pro create an eDrive on my Mac?

There are several reasons that TechTool Pro will not create an eDrive. First, be sure that there isn't already an eDrive installed on your Mac, such as an eDrive from TechTool Pro 5. If so, select Remove eDrive first, and then create a new eDrive.

If TechTool Pro is reporting an error when creating the eDrive such as, "An error has occurred. Run Volume Rebuild on the selected eDrive Destination Volume," try running the Volume Rebuild tool on the destination volume to repair any volume structure problems.

If the error persists, be sure that the volume is not overly fragmented by running 'Preview Optimization' in the Volume Optimization tool. If it indicates large amounts of fragmentation, you might try copying some large files to an external volume, and trying again. Copying the files back to your drive should do so in a way that is more contiguous.

If the 'Create eDrive' button is grayed out, you may need to choose a different destination drive.  If Mac OS X 10.7 'Lion' is installed, and FileVault 2 is enabled, the volume that is encrypted with FileVault 2 cannot be modified, preventing the creation of an eDrive.  To create an eDrive on the internal volume in this case, either partition the hard drive into an encrypted and a non-encrypted portion prior to enabling FileVault 2, or create the eDrive on a volume that is not protected by FileVault 2.  

For external drives, if the Create eDrive button is not available, confirm that the drive is formatted Apple Partition Map or GUID Partition Table.  To check this, you may look at the drive's info in Apple's Disk Utility.

Disk Utility check format