Do those four things in order, and that error window will never appear again. Now go play your game – preferably from that portable drive, but install it from your internal one.
Windows uses a pagefile (virtual memory on the SSD/HDD) to supplement RAM. If the pagefile is disabled or too small, decompression fails.
If you are installing to an old Hard Drive (HDD), it might have "Bad Sectors."
The unarc.dll (Unarc Dynamic Link Library) is a standard component used by repacking tools (like FreeArc) to unpack these highly compressed archives. Error code 11 is one of the most common yet misunderstood failures encountered during this process. While the error message suggests corruption, the root cause is often a complex interplay between software integrity, random access memory (RAM) volatility, and storage media limitations.