So, a few weeks ago i had a system crash again. this time i finally got some decent errors that could turn it into a RMA case and get it replaces. since i couldnt wait for the new disk
i decided to use an old disk.
I inserted the installation disc, followed the installation instructions, formatted the disks, created the partitions manually, everything went just fine.
After installing and updating the system,and installing the raid drivers (earlier post) it was now time to install mdadm and lvm2, to get my data back on track.
it updated the files in /boot/ without any errors, all just perfect..until
I rebooted the system, and got some nasty error (sorry, cant remember which, but it was same second grub started)
No matter what i did, i was unable to get the system up and running again, someting fucked it for good.
anyhow, since the whole installation didnt take more than 15minutes, i just decided to do it all over again.
(repeat this post 12 times… 3 hours later..)
it seems like the disks i borrowed from a friend, was part of an old mdadm raid-5, and since the raid information is stored in the superblocks, it didnt really matter how many times we format the disks – installing mdadm and rebooting the system, would make mdadm recognize the disk and so some naughty stuff to it 
the solution for me was to boot an ubuntu live cd, set up pppoeconf, install mdadm and do a
mdadm –zero-superblock /dev/sdx (be carefull, and be sure its the right disks your fucking with)
it takes a sec, and now the disks is ready for use again. 