Reasons: 1.The screen driver isn´t fully compatible with Win 98 causing system hangs. 2.Microsoft Java Virtual Machine isn´t fully compatible. 3.All other reasons I still haven´t discovered. (It took a week to discover #2 reason!) I hope these issues can be resolved, because there are other valuable improvements. However, if your programs run good now in Win 98 or Win 98 SE, don´t upgrade! I was lucky to have 1970 left on my hdd.