How to Switch between 2 OSes

well i think u will need two computer for that
or may be those virtual computer softwares

without restarting its not possible to boot into another OS like using switch user system in xp but there is a s/w called xosl which gives u some options for people having 2 or more OS..check it out

The only way is to boot into XP and then start Virtual PC or ne other similar s/w and then start win 98 in that s/w (virtually).