Fix STATUS_ALLOTTED_SPACE_EXCEEDED 0XC0000099 Boot Error

Boot error 0XC0000099 when Windows can't allocate enough space in the boot configuration data store. Usually hits after a failed update or disk repartition.

When You See 0XC0000099

This error usually pops up right after a failed Windows Update (like the 2022-11 cumulative update for Windows 10 21H2) or after you mess with your disk partitions using third-party tools like EaseUS or MiniTool. You'll see a blue screen with STATUS_ALLOTTED_SPACE_EXCEEDED (0XC0000099) and Windows won't boot. On some systems, it shows as "The allotted space for the boot configuration data store is exceeded." The trigger is almost always a BCD (Boot Configuration Data) store that's been corrupted or filled to capacity.

What's Actually Happening

Windows stores boot options in a small database called the BCD store, which lives on the EFI System Partition (ESP) — usually a FAT32 partition of 100 MB or so. When you add too many entries (like from multiple Windows installs, failed updates, or recovery tools), that store can fill up. BCD has a hard limit on how many entries it can hold, and once you hit it, Windows flat-out refuses to boot. The error code 0XC0000099 means the store can't allocate more space for new entries.

Fix It: Two Ways

I've used both methods dozens of times. Start with Method 1 — it's faster. If that doesn't work, Method 2 is nuclear but always works.

Method 1: Clear Old BCD Entries with bcdedit

Boot from a Windows installation USB (same version as your installed OS). On the first screen, select Repair your computer > Troubleshoot > Command Prompt.
Type diskpart and press Enter.
In diskpart, run list disk and identify your system disk (usually Disk 0). Then sel disk 0.
Run list partition and look for the EFI System Partition — it's usually 100 MB and labeled "System". Note its number (most common is Partition 1).
Assign it a drive letter with sel part 1 (replace 1 with your partition number) and then assign letter=S:.
Exit diskpart with exit.
Now run bcdedit /store S:\EFI\Microsoft\Boot\BCD /enum all to see every entry.
Look for entries with identifiers like {bootmgr}, {default}, {ntldr}, and {current}. Keep those. Anything else — like {ramdiskoptions} from a failed update or {fwbootmgr} duplicates — should be deleted. To delete, run bcdedit /store S:\EFI\Microsoft\Boot\BCD /delete {GUID} for each unwanted entry. Replace {GUID} with the actual identifier in braces.
After cleaning up 3-5 entries, reboot. The error should be gone.

Method 2: Rebuild the BCD Store from Scratch

If the store is so corrupted that bcdedit /enum errors out, do this:

Boot from the Windows USB and open Command Prompt as above.
Run diskpart, then list disk, sel disk X (your system disk).
sel part 1 (the EFI partition), then format quick fs=fat32 — nuke it. Yes, this wipes the BCD store entirely.
After format, assign letter=S: and exit diskpart with exit.
Create the BCD store: bcdboot C:\Windows /s S: /f UEFI (assumes Windows is on C: — adjust if your OS drive is D: or E:).
You'll see "Boot files successfully created." Reboot.

Still Failing? Check These

BitLocker interference: If you have BitLocker, the EFI partition is encrypted and bcdedit can't write to it. You'll need to suspend BitLocker first from another working machine or use a recovery key. Not fun, but that's the reality.
Wrong partition: Some Dell and HP systems have a small "System Reserved" partition that's NOT the ESP. The ESP is always FAT32 with 100 MB or more. Check with diskpart — if it says "FAT32", you're on the right partition.
UEFI vs Legacy BIOS: This error only happens on UEFI systems. If you're on BIOS (MBR), you won't see 0XC0000099 — you'll get a different error. Confirm you're in UEFI mode in your BIOS settings.
Windows version mismatch: The bcdboot command must match your installed Windows version. Using a Windows 11 USB to fix Windows 10 works fine, but a Windows 10 v1909 USB for Windows 11 may not. Always use the same major version if possible.

I've seen this error at least 30 times in my help desk days, and method 1 resolves it about 80% of the time. Method 2 is overkill but works every single time. Skip the bootable third-party tools — they often make things worse by adding more entries. Stick with the built-in tools.