Thank you for posting in Symantec community.
I would be glad to answer your query.
As per System requirements SEPM installed drive should have minimum 100 GB free disk space.
First we need backup files and recovery file to move SEPM successfully to another drive/machine.
Do you have backup file at C:\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\data\backup folder? If yes, what's the backup size?
Total how many clients are in the network?
Meanwhile refer this article as well:
Disk Space Management procedures for the Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH96214