So i'm upgrading a Compaq Proliant 1600 from 1 CPU to 2 of the same stepping rev etc. Under the device manager it is listed as a "Standard PC" ( hal.dll) looking at Q237556 this sheds no light on the subject of it currently being ACPI complient. I assume that it isnt because the BIOS is E34rev and they are now upto P08 ( which is ACPI comp) SO before i upgrade the BIOS if at all. Can a I just follow Q234558 and change the HAL to MPS Multiproc PC with out a reinstall. ? ? Please advise ... With thanks Paul