I want to know how I can guarantee that grub will leave my MBR alone.
Before I’ve used lilo and installed the boot stuff on a removable usb device.

The reason behind my fear of MBR changes is that my company uses some dumb-ass windows only harddisk encryption that pukes if the MBR has changed and will require me to do a complete reinstall of windows.

Installing the boot stuff on the opensuse root partition (only!) and using EasyBCD to edit the windows boot file adding linux would be a very sweet setup for me. How can I configure this?

You didnt mention whether you are using vista or xp. In any case, during SUSE install, you should come to a GRUB screen. Uncheck MBR and choose custom partition, e.g., /dev/sda2, if this is your root partition. There is also a dialog box below this that says something like “Write generic info on MBR”. Uncheck this!

Since you are planning to use windows as your primary boot loader, you will have to find a way to access /dev/sda2 after install. You can use KNOPPIX live CD. Open a root console and type
“dd if=/dev/sda2 bs=512 count=1 of=mylinux.bin”
Copy the file mylinux.bin to a medium, e.g., floppy or USB memory stick. Now boot into windows and copy this file to C:.
If using XP, use Notepad to edit C:\boot.ini and add the line
C:\mylinux.bin=“openSUSE 11.1”
at the end of the file.
Reboot. You should be able to select either XP or SUSE from the boot screen.