Vista - Update or Install fails "Windows could not update registry data"

I have been trying to upgrade XP Professional to Vista on a Dell Inspiron
5150, bu the installation eventually fails after installing all the files
with an error "Windows could not update registry data in the installation".

The "Upgrade Adviser" found an issue with older driver for wireless network
card, but I installed newer version, and that is now fine.

I have also tried a 'clean' install, rather than an upgrade, and get the
same error - which would suggest it is a hardware/disk/file problem rather
than some existing drivers/apps on the machine.

The ISO DVD is fine and I have verified the Sha checksum.

Any ideas anyone?

cheers.



Sue