This error usually appears when installing a game or software, especially through cracked or repacked installers. It occurs because the installer cannot extract files properly, often due to corrupted archives, antivirus interference, or system issues.
The good news is — it can be fixed with some straightforward steps.
⚙️ Common Causes
- Corrupted game or software installer
- Insufficient RAM or virtual memory
- Damaged unarc.dll file
- Antivirus or Windows Defender blocking extraction
- Hard drive issues (bad sectors)
- Background apps interfering with installation
🛠️ Fix 1: Re-Download or Use a Different Installer
Sometimes the installer itself is corrupted.
Steps:
- Delete the current installer completely.
- Download it again from a reliable source.
- Make sure the download is complete (check the file size matches the original).
- Run the installer again.
✅ Result: Ensures that you’re not using corrupted installation files.
🛠️ Fix 2: Run Installer as Administrator
Lack of permissions can prevent files from unpacking.
Steps:
- Right-click the installer → Run as administrator.
- If prompted by UAC, click Yes.
✅ Result: Grants full access to write and extract files.
🛠️ Fix 3: Disable Antivirus/Windows Defender Temporarily
Antivirus software can block file extraction, leading to corrupted archive errors.
Steps:
- Temporarily disable your antivirus.
- Open Windows Security → Virus & Threat Protection → Manage Settings.
- Turn off Real-time protection.
- Run the installer again.
✅ Result: Prevents antivirus from interfering with file extraction.
🛠️ Fix 4: Replace or Re-register unarc.dll
Sometimes the unarc.dll file is missing or corrupted.
Steps:
- Download a fresh copy of unarc.dll from a reputable source.
- Copy it to:
C:\Windows\System32
C:\Windows\SysWOW64 (for 64-bit Windows)
- Open Command Prompt as administrator.
- Run the command:
regsvr32 unarc.dll
- Restart your PC and try installing again.
✅ Result: Fixes DLL-related extraction errors.
🛠️ Fix 5: Increase Virtual Memory / Page File
Insufficient RAM can cause archive unpack errors.
Steps:
- Press Windows + I → System → About → Advanced system settings → Performance → Settings → Advanced → Virtual memory → Change.
- Check Automatically manage paging file size or manually set:
- Initial size: 4096 MB
- Maximum size: 8192 MB
- Click Set → OK and restart your PC.
✅ Result: Ensures enough memory for the installer to unpack files.
🛠️ Fix 6: Use a Different Extraction Tool
If you’re installing from a compressed archive (RAR, ZIP, 7z):
Steps:
- Use WinRAR, 7-Zip, or PeaZip.
- Extract the archive manually to a folder.
- Run the setup from the extracted folder.
✅ Result: Avoids installer extraction errors caused by built-in unpackers.
🛠️ Fix 7: Check Hard Drive for Errors
Bad sectors or disk corruption can cause unpacking errors.
Steps:
- Open This PC → Right-click drive → Properties → Tools → Error checking → Check.
- Wait for Windows to scan and fix errors.
- Try installing again.
✅ Result: Repairs disk issues that prevent proper file extraction.
💡 Additional Tips
- Ensure the installer path does not contain special characters.
- Avoid installing on external drives or USB drives.
- Close unnecessary background applications before installing.
- Use a fresh system restart before installation.
❓ FAQs
Q1: What is unarc.dll?
A: It is a dynamic link library used to extract compressed game/software files during installation.
Q2: Will reinstalling Windows fix this?
A: Only as a last resort. Usually the above fixes solve the problem without reinstalling.
Q3: Why does this happen with repacked games?
A: Repackers often compress files aggressively, and any corruption during download triggers this error.
Q4: Can antivirus permanently block installers?
A: Sometimes. Whitelisting the installer or temporarily disabling real-time protection usually fixes it.
🎯 Conclusion
The “An error occurred when unpacking unarc.dll, returned error code 1” issue is usually caused by corrupted installers, missing DLLs, or insufficient system resources.
By re-downloading the installer, running as admin, replacing unarc.dll, increasing virtual memory, and disabling antivirus, you can resolve this error and install your software or game successfully.
