Tomorrow is my exam & no SQL / oracle software.

It’s my exams tomorrow of oracle. In which i’ll have to build some database with tables, execute queries, and some PL\SQL block.
My bad luck is my HDD crashed before some days.. and i’m stuck with no working oracle version from 8i to 11g on windows 7 x64. I tried them all.. I can’t log in. Oracle don’t accept “scott” “tiger” .. “system” “system” or “admin” “admin”…
Else, I need some alternative, which is connected to database and I use it for practice. I’m soo nervous.. please help me out.
Answer #1
What do you need?
Answer #2
What do you need?
I need a working sql plus window or an alternative of it.. in which can practice with oracle commands. Just of creating a tables, firing some queries etc.
Answer #3
Uninstall every version of Oracle then install, 10g by following this guide:
http://www.cs.utexas.edu/users/dsb/CS347/Course/oracle_10g_installation.htm
Do not skip anything of the above guide.