I used testdisk (http://www.cgsecurity.org/index.html?testdisk.html
) to fix the partition table. I was unaware of this program but it worked out perfectly.
The partition table error was indeed the cause for my problems... To log into my linux part I used the red hat 9 boot disk to fix my problems... That did not work before I used testdisk because it did not see any proper red hat install while now it did.
To prevent further MBR and boot difficulties (which I experienced before with dual boot systems) I now made red hat 9 boot from floppy...
Easier than I thought...
Thanx for the hint, it seemed to be enough