so my question is: is there a possibility to do (what fixboot in
recovery console does) with a DOS-Tool or an PE system?
you may want to look at
MBRWiazrd (Dos, Win32 & Linux)
or
BootPart (Dos)
or
MBRFix-Gui & MBRFix (win32 only)
honestly I think that mbrwizard is your best bet. Its dos based, although it looks like he also has a linux version so you could integrate this into the unattended linux boot cd if you wanted to.
