The Filename, Directory Name, or Volume Label Syntax is Incorrect
When you try and add another USB external drive to windows backup you get the following error “ The filename, directory name, or volume label syntax is incorrect”.
This message occurs if you have another drive currently assigned to the backup and it is NOT currently accessible. eg. its offsite or you only have one dock attached to the server. To add another disk and get around this error do the following:
1. Open an Administrative Command Prompt
2. Run ‘wbadmin get disks‘
3. In the output of this message locate the external USB drive you want to add to the backup set. The format of the output will be something like:
Disk name: xxxxxxxxxxx
Disk number: x
Disk identifier: {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
Total space: xxx.xx GB
Used space : xxx.xx GB
4. Run the following command copying the Disk Identifier from step 3 at the end of the command:
WBADMIN ENABLE BACKUP -addtarget:{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
5. Answer yes to the prompts.



