If it is an OEM version of the OS there should not be an issue with activation. 
I have a client that has a PE2900 that the server software is reading that Fan 01 is not operating ( 0 rpm) so all fans are no longer redundant and running at high speed. However all fans are running including Fan 01 ... I have swapped fans and still same reading and fast speed. I have troubleshooted this and updated the Bios and Firmware as suggested, no change. Checked connections of fans are all fine. There seems to be only two solutions to this ... either add resistors to the fans to slow them down and allow the system to continue thinking Fan01 is out, or replace the entire mother board to replace the sensor that is apparently gone bad ... First, I think that is crazy there is not a way to replace the sensor, but it is what it is ... I need to know when getting a new motherboard for a 2900 are there different ones that may get me the wrong one ? I looked in the server admin software and could not find a listing for the motherboard exactly ? Here is what is listed and wondering if the first one or last one listed is the motherboard ? If not how do I make sure I get the same motherboard?
Motherboard ID - Please Help