efiling more than 5 tax returns

Can i purchase tt cd, efile 5 tax returns, delete the program, buy a new tt cd and efile 5 more tax returns? If i had to, would i be able to set up a new acct with the same email address, without deleting my original acct? Can i have 2 accts on the same computer even if 1 program has been deleted? I'm reading that there are problems efiling 5 more tax returns with the new cd, that when efiling, message is already efiled 5 tax returns,