So you’re installing a FitGirl repack. Everything looks fine. The progress bar moves. You get excited. Then boom — “Unarc.dll returned an error code” pops up and ruins your day.
Don’t panic. This error is very common. And yes, it is fixable. You just need to understand what’s causing it.
TLDR: The Unarc.dll error usually happens because of corrupted files, low RAM, antivirus interference, or missing system components. Start by verifying files and disabling antivirus. Then check your RAM, disk space, and Windows updates. In most cases, one of these quick fixes solves the problem.
What Is the Unarc.dll Error Anyway?
First, let’s keep it simple.
Unarc.dll is a Windows library file used during decompression. FitGirl repacks compress games heavily. That’s how they make them smaller to download. During installation, your PC must unpack all those files.
If something interrupts the unpacking process, you get an error.
The message may look like this:
- Unarc.dll returned an error code: -1
- Error code: -11
- ISDone.dll error
- Archive data corrupted (decompression fails)
Different code. Same headache.
Why This Error Happens
Here are the most common reasons:
- Corrupted download
- Antivirus deleting files
- Not enough RAM
- Not enough disk space
- Bad sectors on hard drive
- Windows missing system files
- Overclocked or unstable PC
Now let’s fix them one by one.
1. Check If Your Files Are Corrupted
This is the most common cause.
If even one small file is damaged, the installer will fail.
What to Do:
- Recheck the torrent files.
- If available, use “Verify files” in your torrent client.
- Rehash the download.
- If needed, redownload the corrupted parts.
If you skipped this step before, do it now. It fixes many cases instantly.
2. Turn Off Antivirus (Very Important)
Antivirus programs love to interfere with repacks.
They often delete crack files. Or block decompression. Sometimes they quarantine Unarc.dll.
And they rarely tell you clearly.
Steps:
- Disable Windows Defender temporarily.
- Turn off any third party antivirus.
- Add the game folder to exclusions.
- Run the setup again.
After installing, you can turn protection back on.
Important: Always download repacks from trusted sources only. Safety still matters.
3. Check Your RAM
FitGirl installers use heavy compression. That means RAM usage can spike.
If you have only 8GB of RAM and other programs are open, the installer may crash.
Try this:
- Close all background programs.
- Disable browsers.
- Turn off overlays (Discord, GeForce Experience).
- Restart your PC before installing.
If the repack gives a “limit RAM usage to 2GB” option, enable it.
Yes, installation will be slower. But more stable.
How to Test RAM Health
You can use Windows Memory Diagnostic:
- Press Windows + R
- Type mdsched.exe
- Restart and scan
If errors show up, your RAM may be faulty.
4. Make Sure You Have Enough Disk Space
This one sounds obvious. But many people miss it.
Compressed size is not the same as installed size.
A 40GB repack might need 80GB after installation.
Do This:
- Check required space in the repack description.
- Keep at least 20GB extra free space.
- Install on a drive with good health.
If your drive is almost full, errors happen more easily.
5. Install or Reinstall Required Programs
Sometimes Windows is missing important components.
FitGirl installers usually include them. But not always perfectly.
You may need:
- Microsoft Visual C++ Redistributables
- .NET Framework
- DirectX
Install or reinstall these from official Microsoft sources.
6. Check Your Hard Drive for Errors
If your HDD or SSD has bad sectors, decompression may fail.
This is especially common with older hard drives.
Run a Disk Check:
- Open Command Prompt as Admin
- Type: chkdsk C: /f /r
- Press Enter
- Restart if prompted
Replace C with your install drive letter if needed.
This scan may take time. Be patient.
Image not found in postmeta7. Remove Overclocking
Overclocked CPU? Overclocked RAM?
That might be the hidden villain.
Decompression is CPU intensive. If your system is unstable, it will crash here first.
Fix:
- Reset BIOS to default settings.
- Disable XMP temporarily.
- Try installation again.
If it works after this, your overclock is not stable.
8. Increase Virtual Memory
Low RAM plus low page file equals disaster.
Increasing virtual memory can help.
Steps:
- Open System Properties
- Go to Advanced system settings
- Under Performance click Settings
- Go to Advanced tab
- Click Change under Virtual Memory
Set custom size:
- Initial: 8000 MB
- Maximum: 16000 MB
Adjust based on your system RAM.
9. Common Error Codes and What They Mean
| Error Code | Meaning | Most Likely Fix |
|---|---|---|
| -1 | General decompression failure | Recheck files, disable antivirus |
| -11 | RAM related error | Test RAM, enable 2GB limit |
| -12 | Disk write error | Check disk space and health |
| -14 | Corrupted archive | Redownload files |
This table saves time. Screenshot it if needed.
10. The “Safe Install” Method
If you’re tired of trial and error, follow this checklist:
- Restart PC
- Disable antivirus
- Close all apps
- Enable 2GB RAM limit
- Install on healthy drive
- Do not run anything else
Seriously. Do nothing while installing.
No YouTube. No gaming. No multitasking.
Let it finish peacefully.
What NOT to Do
Avoid these mistakes:
- Do not download random DLL files from sketchy sites.
- Do not copy Unarc.dll into System32 manually.
- Do not ignore antivirus warnings blindly.
- Do not install on faulty hardware.
Downloading random DLL files can make things worse. Or infect your system.
When Nothing Works
If you tried everything:
- Test with another repack
- Try installing on another drive
- Update Windows fully
- Consider fresh Windows installation
Sometimes the OS itself is corrupted.
And yes, occasionally the repack itself is broken.
Final Thoughts
The Unarc.dll returned an error code problem looks scary. But it’s usually simple.
In most cases, it’s one of these:
- Antivirus interference
- Corrupted download
- Insufficient RAM
- Disk problems
Work through fixes calmly. Step by step.
Don’t rush. Don’t randomly change system files.
And remember — heavily compressed repacks push your PC hard. Stability matters.
Now go fix that error. Your game isn’t going to install itself.