If Control Panel, Internet (Options?), General tab does not allow start page changing, then (Don't know if its stored under the same area in registry in 98, but,) assuming you are happy editting the registry, try looking for
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main or HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main (sorry can't remember which is correct), and alter the value in Start Page to about
:blank for now - that about
:blank shouldn't have any spaces in it, not sure why forum keeps inserting one.
Failing that, I know WebRoot's
SpySweeper plays around with that area of the registry