Vista Drivers - Unable to install

[jambajamba]

We have an unattended Vista install using WinPE and using setup.exe /unattended:xmlfile - this works well and the majority of our drivers are installed during phase1 (As defined by Windows System Image Manager). However, we have some misc machines that turn up which did some other drivers installing manually as a one off. When logging on as the local administrator account ("Administrator"), the driver installation begins but generally fails with "access denied". I have even tried running the installers with "run as administrator" - but the same thing occurs.

Any thoughts?

Thanks in advance