Firstly, and Unarc.dll are legitimate components of Inno Setup , a free installer for Windows programs. They are not viruses. Their job is to decompress large archives (like .bin or .cab files) during installation.
If you have tried Fixes 1-7 and the isdone.dll isarcextract unarc.dll error persists with your download manager: isdone.dll isarcextract unarc.dll fix download manager