While installing a new server here, I came upon one of the more annoying problems in installs, missing drivers. This is a brand new HP ML150 with Windows 2003 Standard x32, I installed all the drivers that came on the support CD, and did all my windows updates.
Still, the problem remained of two unknown devices with ID ACPI\HPI0002\0 and ACPI\IPI0001\0
After much looking around, I ended up tracking the two items down - they are not located on the CDs, and one of them is not even available for download without calling HP! The files are now located here -> http://www.block.net.au/help/files/HPDrivers.zip
That zip file contains the drivers necessary for most HP Servers with this problem, including the ML150 and ML110 - the readme.txt file is effectively just the instructions of which is which.
One driver has an executable that will install it for you, the other must be done the old fashioned way.
Good luck!
Kieran