Does it start to boot and the logo screen switches to scandisk? It will do this automatically if you don't shut down properly. Does scandisk finish as ok and then continue booting or going back to desktop?
Give more info.
And I assume you mean Windows98 Second Edition?
My wifes computer running win98 v2 keeps dropping out and then runs scandisk. I defragged it hoping this may help but it is still doing it. Any help appreciated.