Hard drives

It sounds as if you want the 40 gb drive to have win2k on the faster computer ; and the 20 gb drive to have win98 on the slower computer.

If that's what you are looking to do, then probably the easiest way (which will take a lot of work), is tobackup all of your data on these two computers and erase the hdd and start over.

The computers are different (one faster than the other) and thus they probably have different hardware drivers.

You're wanting to change the OS on the drives too,which is best done by a clean install.
-----------

If you are only wanting to swap hdds, then go ahead and swap them. If the computers are PnP (plug and play) enabled, then the hardware differences should be dectected at bootup and you should be prompted to insert the drivers.

The best way to swap OS between drives is to purchase a third party software such as
Drive Image by Powerquest
Norton's Ghost by Symantec
and there is Drive2Drive by Future Systems which is the least expensive product at $24.95