Drives (actually- partitions, technically) will not appear in My Computer until they are formatted with a Windows filesystem.

To format the new drive in Win 2K, open the Computer Management application in your Administrative Tools folder. Under the Storage section, choose Disk Management. In the resulting display in the right-hand window you should see both of your drives listed in the upper half of the window, and a colored, graphical representation of any/all partitions on each drive in the lower half of the window.

Right-click on the entry for the new drive in either the upper or lower half of the window (if you hooked the new drive up as the Primary Slave drive, it should be listed as Disk 1) and choose "Format" from the right-click option menu.

One possible catch- if your computer is too old, its BIOS and/or drive controller may not recognize the full 200G capacity of the new drive; if Disk Management reports the capacity of the new drive to be much less than 200G (127G or 132G, for example), this is most likely the problem. If so, a BIOS/motherboard firmware upgrade may be available to fix the limitation.