NERR_RplBootInUse (0X00000A4B): Delete Boot Block Fix

You're trying to delete a boot block but Windows says it's in use. This happens on legacy RPL/RIPL setups and old domain controllers. Here's how to free it up.

I know getting NERR_RplBootInUse (0X00000A4B) when you just want to delete a stale boot block is maddening — especially because this error only shows up on setups most people haven't touched in fifteen years.

The short answer

You can't delete a boot block that has workstations, profiles, or configurations still mapped to it. Windows won't let you. You have to detach every workstation record first, then remove the boot block.

Step-by-step fix

Open Reminst (the Remote Installation / RPL manager). On Windows NT 4.0 Server and early Windows 2000 Server with RPL support, this is the Remote Boot Manager, usually under Administrative Tools or launched by running rplmgr.exe from the System32 folder.
Expand your server, then the Boot Blocks node. Find the boot block that won't delete.
Look under that boot block for Workstations, Profiles, and Configurations. These are the three things the error names. Every entry has to go before the boot block will release.
Delete every workstation record. Right-click each one, choose Delete. Don't skip records that look empty — an orphaned entry with no MAC still counts.
Delete every profile. Same deal. Old profiles left behind by removed hardware are the usual culprit.
Delete every configuration. If any configs reference the boot block, they block deletion too.
Right-click the boot block and delete it. It should go quietly this time.

If the GUI is being stubborn, you can also clear the boot block from a command prompt on the DC:

rplsvc -d -b <boot_block_name>

Run it from an elevated prompt. On NT 4.0 you needed rplsvc in the path — it lives in %SystemRoot%\System32.

Why the error happens

The RPL (Remote Program Load) service keeps a referential integrity check between the boot block and anything that depends on it. Workstations, profiles, and configurations all point back at the boot block via an internal GUID. When you try to delete the parent while children still exist, the service returns NERR_RplBootInUse rather than risk leaving dangling records. That's a sane design — it just becomes painful when the children are ghosts from a machine you decommissioned in 2003.

I've seen this most often on a BDC that got promoted to PDC after the original was fried, then inherited a pile of orphaned RPL workstations nobody claimed. The boot block looked empty in the tree until you drilled into it and found forty entries from a lab that was torn down years earlier.

Less common variations

The boot block is on a different server than the one you're deleting from

RPL metadata can replicate between DCs in the same domain. If you're deleting from a BDC, the operation might be trying to touch a boot block that's homed on the PDC. Run the deletion from the server that actually hosts the boot block.

Replication hasn't caught up

You deleted the workstations on DC1 but the deletion hasn't replicated to DC2. Force replication with replmon or repadmin /syncall, then wait a few minutes and retry.

Service is holding a handle

Stop the Remote Boot service (rplsvc.exe) before deleting. On NT 4.0, net stop rplsvc. On 2000, use the Services MMC. Restart it after the boot block is gone. This clears cases where a stuck session pinned the record.

Corrupt RPL database

If entries won't delete and the service won't stop cleanly, the Jet database backing RPL is probably damaged. It lives in %SystemRoot%\System32\RPL. Back it up, then restore from a known-good copy or rebuild the RPL store from scratch. On a modern network, this is a sign to retire RPL entirely.

Prevention

Delete workstations before their hardware. The moment a machine leaves your environment, remove its RPL workstation record. Future-you will thank present-you.
Audit boot blocks quarterly. On any DC still running RPL (and honestly, in 2024, that should be zero), script a weekly dump of workstations per boot block and clean out anything with no heartbeat in 90 days.
Migrate off RPL. Remote Program Load is a NetBEUI-era relic. If you're still running it because of a couple of ancient thin clients, move them to PXE. You'll never see 0X00000A4B again because the whole subsystem disappears.
Document boot block ownership. Put the owning team's name in the description field of every boot block. When someone asks "can I delete this?" the answer is written right there.

If you're on a modern Windows Server (2016+) and seeing 0X00000A4B, something is wrong with your environment — RPL was removed years ago. Check whether a legacy app or a leftover driver is faking the service, and scan for a rogue DC still running NT 4.0 emulation.