Yes, if you have an IDE port in the new PC, you can just plug it in.
If there is already a drive on the IDE channel, and that one is set to Master, yes, set the old IDe to slave.
I would make a back up of the data on that old IDE drive....you should have another copy of it, on DVD, or on a portable drive, or something.
Win2K on the old disk is not an issue....it will be formatted in NTFS most likely, but, even formatted FAT32 your new PC will be able to read the data off it.
HTH
NXIL.