Error -12 frequently appears when Windows runs out of memory during decompression. This is very common on systems with only 4-8 GB of RAM.

:

By systematically going through these steps, you should be able to resolve the "unarc.dll error code 12" issue on your 64-bit system.

If using a FitGirl or DODI repack, check the box that says "Limit installer to 2GB of RAM usage" at the start of the setup.

Check and set it to a stable range like 6 or 8 . Restart your PC and attempt the installation again. 3. Increase Virtual Memory (Page File)