If you are building a system with a RAID disk make sure you have control over the serial number that windows uses to verify the install.
My file server with the 1.2TB disk had a bad disk the other day in replacing it I had to rebuild the array, this all went fine. But when logging back into windows I got kicked out with a message saying Windows can't validate the license key. It turns out the Windows install is keyed the serial number of the hard disk it is installed to. I guess when rebuilding the array a new serial number got assigned which trashed my install. Fortunately I have been lazy and hadn't moved critical things like my site to the new server yet.
Actually in all the playing around I had to do it turned out that the original hard disk wasn't bad, but the power supply. I would have replaced the motherboard first but the guy at New Type suggested that the power supply would be the probable cause since the hard disk was ok. My boot drive is now an old 80G IDE disk I found while cleaning up one day.
This is the third power supply I have lost in as many months, my laptop, my main PC, now my newest server. They sure don't make them like they used to.