If you chose sda, that means the whole disk, and your previous contents are lost. Do you have backups like mocore said?
If not, you can do a fresh Windows 2000 install to a smaller partition. No resizing needed in that case, which is always iffy with W...
If not, you can do a fresh Windows 2000 install to a smaller partition. No resizing needed in that case, which is always iffy with W...