I was running windows xp installed in AHCI mode (drivers where slipstreamed into custom boot cd) on P35 (ICH9R) chipset. Now I upgraded my motherboard to X58 which has ICH10R and this seems to prevent my system from booting. I have another old copy of xp that used to run in IDE mode and it booted fine discovering all devices, so it seems be down to missing ICH10R drivers in AHCI mode.
I still have my old mobo so I connected it back, took new drivers cd and installed a bunch of *.inf files for ICH10 and they seem to show up on the available list of controller drivers, but that didn't help to boot the system. I thought about changing controller driver in device manger to ICH10, shutting down and connecting it to the new motherboard, but that can make it unbootable with both.
I managed to resolve this. I'm posting a solution in case some with the same problem finds this thread.
I connected my old motherboard with ICH9R on which the system would boot. I installed ICH10R driver (chosing install on the *.inf files). Then in the device manager I chose "update driver", unchecked "compatible devices only" and selected ICH10R AHCI from the list. After confirming I shut down, put the disk into new motherboard and it booted, discovered all remaining hardware and works perfectly.