Not quite sure what you are asking. The best way of linking them together into a mini network would be to use your router. You can network Win98 pcs with Win XP pcs.
If you are asking whether you can use wireless as well or instead of a wired network, yes you can.
And yes, you can repartition hard drives without the need to format. The best known one is Partition Magic, a commercial program, but there may be freeware ones as well. ALWAYS back up your files before repartitioning a drive.