You have to install them into different partitions. If you have only one drive and it's only one partition, you have to repartition it into two. You have to either repartition/reformat it and reinstall Win98 or use something like Partition Magic to resize your existing one if you don't want to reformat. After that, just boot off the W2K CD and point it to your 2nd partition (or drive if you have 2).