Alex Ruben
How To Fix Checksum Mismatch Error in Unarc.dll for Fitgirl and Dodi Repack (2025)
If you’ve ever tried to install a FitGirl or DODI repack game and hit a wall with errors like “Does Not Match Checksum” or “Unarc.dll Error Code -12,” you’re not the only one. Sometimes, these errors pop up out of nowhere, and it’s honestly frustrating because they seem to come from nowhere and mess up your install at the worst moment. This guide scratches the surface of common fixes that actually work in some setups, and will hopefully get you back on track without too much hassle. Basically, these steps aim to fix corrupt DLL issues, setup virtual memory right, and ensure your system is ready for those hefty unpacking processes of big game files.
How to Fix Does Not Match Checksum Unarc.dll Error Code 12 in Windows
Fix 1: Get the correct DLL files and put them where they need to be
It’s kind of weird, but replacing or ensuring your DLL files are correct can actually fix the checksum errors. Those DLLs are tiny but crucial — they handle the unpacking process and checksum validation. On some machines, this fails the first time, then works after a reboot or reinstalling the DLLs. So, download isdone.dll and unarc.dll from reputable sources, like DLLMe – IsDone.dll and DLLMe – Unarc.dll. Once downloaded, the extraction step is important because sometimes files come zipped or in slightly corrupted states. Right-click each file, choose Extract All…, and pop them onto your Desktop for easy access.
Copy DLL files into the system folder
- Navigate through This PC > Local Disk (C:) > Windows > System32. If you’re on a 64-bit system, you might also want to copy them into SysWOW64 folder, just in case. That’s usually at C:\Windows\SysWOW64.
- Drag and drop the
isdone.dllandunarc.dllfiles into the folder. Windows will ask for permission—hit Continue or Yes. If you get permission issues, try running your Explorer or command prompt as administrator next time.
This kicks the DLLs into the system, which can help resolve checksum validation errors during the unpacking phase. Sometimes, Windows stubbornly keeps old or corrupt DLLs, so copying fresh ones makes a noticeable difference.
Fix 2: Tweak your virtual memory (paging file) settings
Because of course Windows has to make it harder than necessary, but setting your virtual memory right can actually stop these checksum errors from happening again. When unpacking big game files, your drive usage spikes, and if your virtual memory isn’t optimized, that’s when errors pop up.
- Press Windows + R, type
control, then press Enter – this opens the Control Panel. - Click on System and Security, then System.
- On the left sidebar, click Advanced system settings. The classic System Properties window opens.
- Under the Advanced tab, click Settings under Performance.
- Switch to the Advanced tab and hit Change under Virtual memory.
- Uncheck Automatically manage paging file size for all drives. Then select your C: drive below.
- Choose Custom size.
- Set the values based on your RAM — here’s a rough guide:
- 4 GB RAM: Initial Size: 2048, Max Size: 4096
- 8 GB RAM: Initial Size: 4096, Max Size: 8192
- 16 GB RAM: Initial Size: 8192, Max Size: 16384
- 32 GB RAM: Initial Size: 16384, Max Size: 32768
- 64 GB RAM: Initial Size: 32768, Max Size: 65536
- Click Set, then OK. Restart to see if errors still pop up during unpacking.
On some setups, this can be a game-changer because it gives your system the right breathing room—kind of like adding a buffer so files get verified or extracted smoothly without checksum errors flying around. Not sure why it works sometimes, but hey, it’s worth a try.
Fix 3: Install all relevant Visual C++ Redistributables
Missing the right runtime libraries for C++ can cause DLL errors during unpacking—so updating or reinstalling the Visual C++ Redistributables is another way to go. Not everyone thinks about this, but it’s a thing.
- Download the all-in-one Visual C++ Redistributable Runtimes from TechPowerUp. It’s bundled, so it saves some hassle.
- After it downloads, right-click and choose Extract All…, then run the
install_all.batfile. You’ll probably get a command window flickering, and it might ask for administrator rights—let it do its magic. - If any install prompts pop up, agree and wait for it to complete. This can fill gaps that DLL errors depend on.
This is especially helpful if you’ve installed the game on a fresh Windows install or recently updated your system. It’s one of those background things that might fix errors you didn’t even realize were related.
Fix 4: Restart, reassess, and try again
When all else fails, it’s stupid but sometimes rebooting after making all these changes helps Windows settle things. Then try re-downloading or re-launching the installer. Sometimes the unpack process just hiccups once, and a quick restart sorts it out.
Extra tips & troubleshooting
Still seeing the same errors? It might be worth checking your antivirus settings — some AV programs block or quarantine DLLs, especially if they’re freshly copied. Also, verify your game files if using platforms like Steam or Epic, because sometimes an incomplete or corrupted archive causes these checksum failures right from the start.
And if newer updates or patches for the game or repack are available, grabbing those is a good move. Most checksum errors are caused by incomplete or mismatched files, so keeping everything fresh helps.
Wrap-up
At the end of the day, these fixes target the common problems: bad DLL files, insufficient virtual memory, or missing runtime libraries. They’ve helped a few friends get through tricky repacks, so worth trying all of them before giving up. These suggestions are kind of a hodgepodge, but hey — corruption can be stubborn.
Frequently Asked Questions
What if errors still pop up after all this?
Check that your Windows is fully updated and that your hardware is within the recommended specs. Sometimes, hardware issues or outdated system drivers cause strange errors too.
Can I use these fixes for other game errors?
Yes. Most DLL errors or checksum issues are similar across different game setups, especially if they involve unpacking or manual installs. These steps touch the common pain points.
Is it safe to download DLL files from random sites?
Only grab DLLs from reputable sources like DLLme or trusted tech sites. Downloading DLLs from sketchy pages can lead to malware or worse, so stick to well-known repositories or get them from official Windows updates.
Summary
- Download DLL files from trusted sources and copy them into System32 or SysWOW64.
- Adjust virtual memory for your system to avoid unpacking hiccups.
- Install all relevant Visual C++ Redistributables to fill runtime gaps.
- Reboot, reattempt installation, and watch for errors to disappear.
Final word
Hopefully, this sheds some light and saves a few hours of frustration. Fixing DLL or checksum errors is kinda trial and error sometimes, but these are the common fixes that rolled for others. Fingers crossed this helps!