Sorry, there is no way to change the ''log'' folder once you have already installed HP-synchronizer Server.
It IS possible, although tricky and prone to error if you UNINSTALL your current HP-Synchronizer and either re-install it or upgrade to the latest version (12.53 SP1).
This involves making a full Postgres DB backup, uninstalling EVERYTHING related to HP-Sync and then re-installing the SAME version of HP-sync with a blank Postgres DB and then restoring it from the backup -- THIS IS EXTREMELY PRONE TO ERROR!
You could also backup each link with sync-data (to a ZIP), then restore them individually into the blank Sync-server.
If you have an older version than 12.53/SP1, the sync-data upgrade is fairly easy and happens automatically, AND you can dictate the ''D'' drive for the HP-Sync Server install drive instead of ''C'' (keep the rest of the path the same).
If on the other hand, you already have 12.53/SP1, it is much more difficult to uninstall/re-install the SAME version and get the data to come in, since there is no way to easily install while using the same back-end Sync-data database. (but there is a way, though - but very tricky).
**Disk Space Method (VM):**
Why not just increase the drive size for Drive C:? On a VM it is very easy.
**Scheduled Job Method:**
Another thing people do is to have a scheduled job/batch that purges or moves the logs on a regular interval out of the C:... log folder to somewhere else.