Does anyone know or have experience installing an HP array controller in a standard PC? I'm interested if it would be possible to use a P400i with a SAS-SATA cable using standard Western digital drives.
I haven't done it personally, but so long as you have the right slot, cables, drives the controller supports, and a driver for the OS you intend to run it should work fine. The ProLiant RAID controllers do not have any reliance on being installed in a ProLiant server computer.
The driver CD that comes with the controller probably won't work on a white-box PC but you should be able to use the ROM BIOS interface (HP calls it the "ORCA" interface). The P400 won't offer this ROM BIOS interface prompt unless it detects supported drives attached.