Plextor drives are compatable with MSI motherboards only if you get the ATAPI version of the drive. The SCSI option will not work unless you add a special SCSI card to adapt the drive to the motherboard.
ATAPI is the acronym of the cd drive's interface. As long as you have an IDE interface availablethe drive will work.
Becareful with the faster Plextor drives which require DMA support. If you have an older motherboard, older then ~4 years, you might not be able to enable this support and take advantage of ths higher speeds of the drive. (It's enabled in Control Panel/System/Device Manager tab/CD-ROM/Settings...)