total disk (as seen in bios) 180GB
total disk as seen in partition section of install 129.97GB (=131700 MB shown by partition program == 50GB lost) .. so the translation from 1024 to 1k is not the culprint..
130GB is the space BEFORE installation of windows so windows is not the culprint for this loss..
Ok, that was the trick! Thank you for pointing it out!
I had not doublechecked the size of partition I could create after installing windows (installcd was XP-sp0) and updating servicepacks. Now with sp3 installed it allowed me to create a new partition of 133,4GB (C: 34GB E:133,4 total ~167,5GB )