'on boot up of win98 ... crashes'...
I would wager that it is caused by multiple issues, some of
which easily solved, others not.  General things maybe to
investigate:
..msconfig,  startup tab, in mine (win98FE) there are 30 or
   so items.  I have all but 8 or so unchecked, and things
   which have to load at startup I put in a batch file w/
   full path, run from a dos box.
..The antivirus I use many days crashes but I take it as
   a unremediable issue since coding any such large program
   is bound to let remain subtle errors.  I have win98 set
   to start from a dos menu, so I can run scandisk c: before
   the next boot to minimize errors.
..Many maintenance issues can minimize crashes.  defragging daily
   before shutdown, putting temporary internet files and the pagefile
   on a seperate partition, using an alternate browser (firefox in my
   case which I set its cache to c:\cache so I can clear it out
   after visiting large-paged sites) which may crash less,  keeping
   c:\temp or c:\windows\temp empty, being sure icons in the lower
   right corner are only there if absolutely necessary, etc...
..If you are certain your startup issues (crashes JUST at startup?)
   are more than suggested by the above you could post more specific
   details as to the exact error messages and when in the boot process
   they occur.  Otherwise, there are programs such as bootLogAnalyzer (bla)
   which can (booting to logged)  find programs that may be at issue.

Much I've left out but there is a lot to cover...

Jeff Bouquet