scrambled partitions

Can anyone help me here ??, i am building a W2K server for my home lab. I created a a single partition on the HDD and install into that. The rest of the disk is unpartitoned. After i install SP2 and reboot the partition is all scrambled up. Instead of booting to c:\ it is looking for D:\winnt…
Can anyone advise as to what is happening here and whether they have seen this before..
Thanks in advance..