^^
it is ALWAYS and i mean ALWAYS recommended and its a MUST to install any other OS onto a separate partition..
btw, wat OS u wanna giv a try..? I cant recommend u jus abt any OS unless u DONT specify for wat purpose u wanna hv tat OS installed..
U can try
1.) Linux OS (ofcourse its installation procedure is a bit complicated for most newbies but at the same time the MOST STABLE OS),
2.) Windows Vista
etc...
Cheers n e-peace...