This file is part of a third-party installation library, often used by commercial installers (such as those created by Inno Setup or specific repackers) to handle the decompression and unpacking of large archives. When you install a large game, the data is often compressed to save space. The installer uses ISDone.dll to "unpack" that data onto your hard drive.
By following this guide, you will resolve the isdone.dll error without exposing your Windows 7 64-bit system to malware. Safe computing remains more important than a quick fix. isdone.dll download windows 7 64 bit