You can buy DriveImage,
<a href="http://www.powerquest.com/driveimage/" target="_blank">http://www.powerquest.com/driveimage/</a>
which is supposedly very good. Not sure about doing it with Win98 - you need to get the bootsector copied, as well as the data. In the good old days you would just type "sys D:" but I'm not sure how you would do it now.