Sounds like ye olde AHCI/non-ACHI issue. In the Bios of the new motherboard, make sure you have the SATA controller set to the same as the old one - it's usually under some heading such as Integrated Peripherals, and may be called "SATA Control Mode" - the options will usually be IDE, RAID or AHCI. You'll probably want either IDE or AHCI - whichever one is selected now, try the other
Also, you sure it's not an ASUS P5N-T? I can't find any reference to an MSI board of that name.