Did you initiate a format? I don't know how your PC came configured, but some manufacturers are using hidden partitions to initiate a 'factory restore'. But since it sounds like your OS is on the 150GB Raptor, I don't think that is the case. Be sure that you have all service pack updates installed, then go back into Dsk MGT and reformat and initialize the drive.
you can't easily. I was finishing the thread so I could shout at you to undo the dynamic setting. unless you are in a server environment all it will do is make life miserable. Just go back into DM and kill the dynamic partition and reformat. you'll be glad you did.