I have windows XP - Home edition on one computer- I used the update disk ( legal copy) on another computer running Windows 98- It installed ok- was able to run for 30 days than I had yo pay for activation which I was unaware of. I was not trying to do anything illegal. I thought it was ok to put the OS ob 2 of your own home computers. MY question is " how can I reformat the HD and revert back to Windows 98" or get rid of windows xp on and revert back too Windows 98. On the computer ( which requred activation); I hit the F* key and got to what I thought was the MS Dos system. When I tried to format the HD; it said the drive is mounted and locked and wouldn't do the format. Thanks for any help given.