Well, system is up and working.

-> memtest revealed a bad RAM stick ...

Below a picture of the cause-of-all-evil:

Below: Neopc beta

I still have a lot of work todo ... but everything's working.

Two strange things: WinXP installation hehaved different (again) and I got two BAD_POOL_CALLER bluescreens ... well, I raised the DIMM voltage ... seemed to help.