log in error - after new installation

[draugluin]

Okay, now I know, my old passwords are encrypted with MD5.

How can I persuade my new database, to use this too ?

Or the other way around: how can I set the new database, so that it encrypt the passwords at the same way ?
The only thing I want is, that I can copy the old encryptet passwords to the new database, so that it works.... every user should be supposed to log in at the new site.
*sigh*