Q: Does this error mean my CPU is defective? A: Rarely. CPU errors usually cause BSODs. Error -7 is almost always RAM, disk, or software.
Q: Can I just delete ISDone.dll from my system? A: Never. That DLL is part of the installer. Deleting it will break Inno Setup entirely.
Q: Why do repacks cause this more than official installers? A: Repacks use extreme compression ratios (like LZMA2 with dictionary sizes over 256MB). This demands more memory stability than standard installers.
If you’ve ever tried installing a large PC game (from GOG, FitGirl, or other repacks) and got a frustrating error message saying:
…you’ve faced one of the most common installation blockers on Windows. isdonedll error unarcdll error7 best
If you have tried everything above and Error -7 persists at random percentages (e.g., 12%, 45%, 88% but never the same spot), you likely have faulty RAM.
Unarc.dll does not use standard CRC checks for every block. One bad stick of RAM will corrupt the data mid-flight.
How to test:
Fix: Remove the bad stick or replace your RAM. Until then, reduce your RAM speed in BIOS (e.g., from 3200MHz to 2133MHz) to stabilize the unpacking. Q: Does this error mean my CPU is defective
Safe Mode loads Windows with only the essential drivers and services. This prevents background applications (like aggressive antivirus tools or RAM-heavy apps) from interfering with your installation.
How to do it:
Inno Setup (which powers ISDone/Unarc) has a known bug: it hates non-English characters in file paths. If your Windows username contains accented letters, Cyrillic, or Chinese characters, the temp decompression path becomes corrupted.
Solution:
Additionally, go to Control Panel > Region > Administrative > Change system locale and check Beta: Use Unicode UTF-8 for worldwide language support. Reboot. This forces Windows to handle all file paths as UTF-8, eliminating the path corruption error.
If none of the above work, try:
Final note: If you keep getting Error 7 with ISDone.dll or Unarc.dll, the problem is almost never the DLL file itself — it’s either faulty RAM, corrupt download, antivirus interference, or lack of system resources. Start with RAM testing and antivirus disable — that solves 80% of cases.