If you're running on Windows, you can change the Internal password. Here is what you need to do:

1) get the exact path of the pwd.ora file (i.ewddata.ora)
2) Using command line, type
ORAPWD FILE= PASSWORD= ENTRIES=

For example:

orapwd file=e:\oracle\ora81\database\pwddata.ora password=oracle entries=5

I ran into this problem a week ago while working on a client's database whose DBA did not want to give out the Internal pswd. I found this on Metalink and it took care of the problem.

Try it yourself. Good luck.