I'm going to repeat this for the third time.
Don't mess with the unity folder.
No buts. No excuses. If you have too small of a harddrive, you're not qualified to use PD. It's that simple. PD was created with assumption that people now have bigger harddrives. "I can't afford another HD now." is not a valid excuse here.
Software minimum requirements specifies minimum of 40GB of free space for unity.