What is the isdone.dll Error? The isdone.dll error (often accompanied by "Unarc.dll returned an error code: -1") is a common installation failure in Windows. It typically appears when you are trying to install large software packages, games, or repacked setups (e.g., from FitGirl, Razor1911, or other repackers).

If you continue to see the error on multiple installers, – it is the most common hardware cause.