torsten, its time you apply yourself now instead of running here.
google will link you to many pages that describe these issues with verbose how tos.
spend some time using google and apply some brainjuice.
geek culture isnt really pc tech help.
http://www.ehow.com/how_6031_change-master/slave-designation.html
http://www.pcmech.com/show/harddrive/43/
http://www.short-media.com/review.php?r=209
http://www.seagate.com/support/kb/disc/ref/jumper_settings.html
if you get stuck, then ask a question relating to your problem.
If your going to ask a question as well provide more information.
do you have IDE, EIDE, ATA or SATA etc..
how many drives have you got, what kind of motherboard etc..