Excel always configures & HKCR\.aw access denied

I am trying to debug an annoyance with Excel - it has started including a "Configuring..." and an "...installing.." every time it launches. This is accompanied by an Event Viewer entry:

- System
- Provider
[ Name] MsiInstaller
- EventID 1004
[ Qualifiers] 0
Level 3
Task 0
Keywords 0x80000000000000
- TimeCreated
[ SystemTime] 2012-07-30T21:25:32.000000000Z
EventRecordID 16911
Channel Application
Computer gwb
- Security
[ UserID] S-1-5-21-2037688818-723828979-1879572323-1001
- EventData
{91140000-0011-0000-0000-0000000FF1CE}
ProductFiles
{E5EE9C9D-798D-4D1D-ABF2-32EC15820B2F}
HKEY_CLASSES_ROOT\.aw\
(NULL)
(NULL)


In regedit, however, I am told access to the key is denied. I cannot view permissions but I am told (untruthfully) that I can change permissions. (I'm logged in as an administrator of the system and UAC is off.)

[edit]Google search says .aw file extension used by MSOICONS.EXE. Just for jollies I tried to execute it but it's reported as not a valid win32 application.[/edit]

Now what?

Thanks.

George