I'm imaging in a multiboot environment with PXE

First partition is a Linux Bootloader is GRUB.
Second partition is Windows XP
When registering the Windows Box with zwsreg the zis info is written successfully.
But after that the GRUB is not working.
The zisd overwrites the same sector grub is using (I think sector 6)
Is there any workaround (like changing the sector for zis) ??