k,
this is the way to go,
u can try
system/manager
scott/tiger
but first u need to make sure that oracle instance is running if it's not running u wouldn't ever be able to connect SQL,
If it's not running then also let me know i'll tell u hw to do that also.
and pls next time let me know ur system config also...
hope this works(But i think u have instance or memory problem coz scott/tiger should work)