XP SP3 won't install? Back to the command line!

After my post back in May reporting no problems with the installation of XP SP3, it was inevitable that I would come across a machine that wouldn't play ball.

A client's XP SP2 machine was reporting errors during the Registry backup phase, complaining of "access denied" to the keys of "HKCR\MsTscAx.MsTscAx" and "HKCR\MsRDP.MsRDP" and some of their numbered duplicates.

The tech had chosen to ignore the errors, so allowing all the file updates to proceed, unfortunately only to be rolled back at the very end of the update process. Thankfully, as he'd also chosen not to take notes of the message details, "%SystemRoot%\svcpack.log" provided me with a full list. Trying to view the errant keys with RegEdit also reported the same error and attempting to repermission them did the same.

There are all sorts of misleading reports on the Web, most of which suggest hacking around while in "safe mode". In fact, Microsoft KB article 949377 provided the answer with its "method 3". Running "subinacl.exe" as suggested on each key solved the problem, allowing SP3 to install itself with no further issues.

Whilst it remains a mystery what caused these keys to become inaccessible, there are a number of discussions on the Web suggesting these particular keys often cause problems. It's amusing that one of MS's own products seems to have caused the difficulty.