I can't delete C:\Config.Msi\75ce84f.rbf

It's not causing any problems but it's a mystery I'd like to solve, preferably before the next reboot because it's scheduled for deletion then (see pendmoves).

• it's not readonly, system or hidden
• it's not in use by another process (according to Process Explorer)
• the NT security permissions aren't the problem either - I am the owner and have Full Control ; as a double-check, the Effective Permissions tab shows that I have permission to delete.

Yet trying to delete the file gives "Access is Denied" from both Explorer and cmd. I can however rename it or move it to another folder on the same drive. I can also read it and Virustotal says it's clean which is what I would expect (it's just a Windows Installer temp file - a copy of some DLL I think). The relevant line from Process Monitor is:

6:52:14.3726983 PM  112 Explorer.EXE    SetDispositionInformationFile   C:\Config.Msi\75ce84f.rbf   CANNOT DELETE   Delete: True    Write   1232

Background: I'm using XP SP2. I recently repaired my Adobe Reader installation to make it the default browser plugin again instead of Foxit. (there seems to be no UI to do it otherwise?) So the installer did its thing and then asked to reboot. As is my habit when rebooting is inconvenient I declined the offer and ran pendmoves to find out what files the installer had scheduled to move / delete. It wanted to delete two files with .rbf extension (rollback files) located in C:\Config.msi\. (this applies to both even though I've been speaking about one). So I tried to delete them manually and couldn't.

Does anyone have any ideas what could be preventing deletion? (and I don't think it's malware even though I'm not running AV at the moment)