The most common reason you are seeing this error is that you are trying to install a program—often a large video game or a repacked software suite—that uses ARC compression to squeeze file sizes down. The installer needs unarc.dll to unpack the files onto your hard drive.
If you absolutely need a copy, extract it from a known good installer of WinRAR, 7-Zip, or a Microsoft-published game you legally own. Then, verify its digital signature and scan it with Windows Defender. unarc.dll download microsoft
Before downloading any file, it helps to understand the exact error you are facing: The most common reason you are seeing this
No, there is provided by Microsoft . This file is typically bundled within the installer of the specific application you are trying to run. Then, verify its digital signature and scan it
Low disk space or limited virtual memory (paging file). Official Recovery Methods