Fix ERROR_INVALID_MINALLOCSIZE (0x000000C3) on Windows

You try to launch an application — maybe something old like a legacy ERP client, maybe a freshly compiled C++ tool — and Windows throws back: "The operating system cannot run %1" with error code 0x000000C3. The error text spells out ERROR_INVALID_MINALLOCSIZE.

What's actually happening here is that the program requested a minimum memory allocation size, and the kernel's MmAllocatePagesForMdl or a similar low-level allocator rejected it. Usually this comes down to a mismatch between what the app expects and what the system's MmMinimumPageSize registry entry allows. Or the registry key itself got corrupted — I've seen this happen after a failed Windows update or a third-party memory cleaner gone rogue.

Let's walk through the fixes from quickest to most thorough. Stop when the error goes away.

First fix — 30 seconds: Check and clear the registry entry

Most cases of 0x000000C3 are caused by a single registry value that shouldn't exist in the first place. Open Registry Editor (regedit) and navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

Look for a value named MmMinimumPageSize. If it's there, right-click and delete it. Don't change anything else. Reboot.

Why does this work? That key was used in very early Windows NT builds to tweak paging behavior — but starting with Windows 2000, it's ignored by the kernel. Its presence often means some ancient setup app or a misconfigured driver left it behind. The kernel sees it, gets confused, and spits out 0xC3. Deleting it tells the kernel to fall back to its own safe default.

Real-world trigger: I've seen this on Windows 10 20H2 and Windows Server 2019 after running an old Oracle Forms installer. The installer writes that key, then any subsequent program launch fails with 0xC3.

Second fix — 5 minutes: Repair the Memory Management subkey

If deleting MmMinimumPageSize didn't help, the Memory Management key itself might be corrupted. You'll need to restore it from a backup. No backup? No problem — the system keeps a copy in the ControlSet001 hive.

Open Registry Editor and compare these two paths:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Memory Management

If CurrentControlSet's version has missing values or different data than ControlSet001, delete the entire Memory Management key under CurrentControlSet, then right-click ControlSet001\Memory Management and choose Export. Save the .reg file. Double-click the .reg file to import it back under CurrentControlSet.

Reboot. The kernel now reads the clean copy from ControlSet001. This fix handles cases where a driver update or a corrupt disk write damaged the active control set.

Skip this if both keys look identical — you're wasting time.

Third fix — 15+ minutes: System File Checker + DISM

When neither registry fix works, the problem is systemic — kernel image corruption, bad page pool headers, or a compromised ntoskrnl.exe. This happens more often on systems that survived a BSOD-induced power loss.

Boot into Safe Mode with Networking. Open an elevated Command Prompt (right-click, Run as Administrator) and run:

sfc /scannow

Let it finish. Then run:

DISM /Online /Cleanup-Image /RestoreHealth

Both commands can take 10–20 minutes. DISM will pull fresh system files from Windows Update if your internet is working. If it fails, you'll need a Windows installation media — insert it and run:

DISM /Online /Cleanup-Image /RestoreHealth /Source:D:\sources\install.wim /LimitAccess

Replace D: with your media's drive letter.

After both complete, reboot normally. If 0xC3 still shows up, the simplest explanation is a memory hardware issue — run mdsched.exe from the Start menu and let the memory diagnostic run. Faulty RAM can corrupt page allocation metadata without triggering the more common memory errors.

When to give up and reinstall

Look, I don't say this lightly. But if you've done all three steps and the error persists on multiple different applications — not just one — your Windows install is likely borked at a level no registry edit can fix. Back up your data and do a clean install. It takes an hour, and you'll waste less time than chasing a phantom registry ghost through every subkey.