Vista SP1 stalls after reboot

[MobileTechie]

I've had a PC in, fixing a problem with an app continuously trying to install at startup which is now OK. I noticed it had no SPs installed so tried to install SP1. It works up to the point where it reboots and then you get the black screen with the number of files counting up it then gets stuck at about 30000 out of 90000 and never moves on. After that it will not reboot and has to be restored.

There is nothing in the logs to indicate why this is happening. All other updates work fine.

I can hand it back with no SPs with the "job done" as such but this isn't really satisfactory.

Any pointers guys? If necessary I can replicate it and come back with the exact file number it stalls on.

[Cambridge PC Support]

I know you've done these already but:

o test memory
o test hdd
o install System Update Readiness Tool
o sfc
o run SP1 from hdd
o empty Software Distrib
o malware/rootkit check

[MobileTechie]

Yeah I've tried all those.

The error is this: !!0xc01a001d 29689/94009 (\Registry\Machine\COMPONENTS\DerivedData...)

I've searched on it and the solutions always seem to involve a reinstall.