Alex Ruben
How To Resolve FitGirl Setup ISDone.dll and Unarc.dll Errors in 2025
If anyone’s tried to install a FitGirl repack and suddenly runs into those dreaded ISDone.dll and Unarc.dll errors, you’re not alone. These errors pop up out of nowhere, usually when the game files are huge or your system hits a wall trying to process the decompression. It’s kinda frustrating because it kills your install right at the worst moment. The good news is, there are a few tricks that can help you bypass or fix these errors without banging your head on the desk. Basically, these fixes are about fixing memory issues, replacing corrupted DLLs, or tweaking your virtual memory settings so your PC can handle the heavy lifting. Once it works, your game should install without crashing — or at least it’ll be a lot less annoying. Anyway, here’s how some users managed to get around it, with some real-world tweaks involved.
How to Fix ISDone.dll and Unarc.dll Errors During FitGirl Repack Installation
Method 1: Download and Replace Problematic DLL Files
This way works when the DLLs are missing or corrupted. Many times, these errors are due to faulty DLLs in the system, so replacing or registering fresh ones does the trick. First, grab fresh DLL files from reliable sources (because of course Windows has to make it harder than necessary). Once downloaded, you’ll copy them into the C:\Windows\System32 folder. This forces Windows to use the new versions instead of whatever’s broken or missing. Just remember to run your file explorer as administrator so you have permission to copy files into system folders.
- Download ISDone.dll and Unarc.dll.
- Right-click those DLL files and choose Extract All to unpack if they’re zipped, then drag and drop.
- Open File Explorer as administrator: right-click on it and pick Run as administrator.
- Navigate to C:\Windows\System32 (for 64-bit systems, also consider copying to C:\Windows\SysWOW64 since some DLLs are 32-bit).
- If prompted for admin permissions, click Continue.
- Paste the DLL files here. Might be worth re-registering them using
regsvr32command if issues persist, but copying usually helps.
This usually helps if the errors are due to missing libraries. On some machines, this step resets the DLLs and prevents the install from crashing.
Method 2: Boost Virtual Memory (Paging File) Settings
This is kind of weird, but a lot of installation errors are just because your system runs out of temporary memory to handle large files. Increasing virtual memory (or paging file) often solves the problem, especially for bigger game files. Here’s how to do it:
- Hit Windows + R, type
sysdm.cpl, and press Enter. - In the System Properties window, click on the Advanced tab, then hit Settings under Performance.
- Go to the Advanced tab again and click Change… under Virtual Memory.
- Uncheck Automatically manage paging file size for all drives.
- Select your C:\ drive, then choose Custom size.
- Input values based on your RAM. For example, if you have 8 GB RAM, try starting with Initial size: 4096 MB and Maximum size: 8192 MB. For 16 GB, double that.
- Click Set, then OK all the way out and restart your PC.
This tweak helps Windows allocate more temporary memory for decompression and installation tasks. Not sure why it works, but on certain setups, it just stops the errors from happening. If the system crashes again or errors persist, bump up these values a bit further or try redoing the setting after a reboot.
Method 3: Update or Reinstall Visual C++ Redistributables
Because of course, missing or outdated Visual C++ runtimes can cause DLL errors during heavy processing. This is especially true if the unpacking process involves decompressing complex files which need runtime support. You can fix this with a quick install of the latest Visual C++ Redistributables bundle:
- Head over to Download Visual C++ Redistributable.
- Select the latest supported version for your system (usually x86 and x64).
- Run the installer, and if you get prompted, select Repair or just install it fresh.
- Reboot after installation — sometimes these files need a nudge to register properly.
This step keeps your system updated with the necessary runtime components. On some setups, outdated or missing runtimes trigger those DLL errors like crazy.
Extra Tip: Make Sure Your System is Up to Date
Another thing, keep Windows in check with the latest updates. Outdated systems tend to cause conflicts, especially with large decompression tasks. Check under Settings > Update & Security > Windows Update and install any pending updates. That often clears up weird errors without much fuss.
Summary
- Replace DLL files in system directories
- Increase virtual memory via system settings
- Update or reinstall Visual C++ redistributables
- Ensure Windows is fully up to date
Wrap-up
Fixing ISDone.dll and Unarc.dll errors can be a pain, but tweaking DLLs, virtual memory, and runtimes together usually does the trick. Sometimes, just copying fresh DLLs is enough; other times, you need to give your system a bit more breathing room. Not sure why, but these tricks have helped on different setups, and maybe they’ll help yours too. Just keep in mind that these errors often come down to insufficient memory or corrupted files, so focusing on those areas is a good start. Fingers crossed this helps — good luck!