[Typo3] cannot use BE at fresh installed typo3 quickstart

[Mikkel Wied Frederiksen]

Hi.

I've just installed TYPO3 quickstart 3.8.0 on my server.
I'm running windows XP SP2, apache 2.0.54, php 5.0.4 and mysql 5.0.15.

The 1-2-3 installation works perfect, but when i try to log in to the 
backend, i get the message, that my username and/or password is wrong. i 
HAVE enabled both javascript and cookies, and i've crosschecked the 
username and password in the mysql database. i've tried loggin in with 
firefox 1.0.7 and with IE 6.0. no luck.

then i removed the TYPO3 lib compleately, and removed the DB, and 
installed the 3.7.1 quickstart instead. and quess what happened. yeah 
you're right, exactly the same. nothing but the same stupid error message.

not php and/or mysql messages appered, so is should work. so what do i 
do now, please help.

Best regards
Mikkel WF