After install of WinXP on another partition Win2k3 doesn't boot anymore.

Hello Experts,

I have had a test-installation windows server 2003 which i really have to access now.
Last week i needed a windows xp installation so i decided to install it on another partition.

After installation windows xp run perfect.

Now in the boot menu, windows server 2003 appears, but does not boot. If i choose it, the pc does reboot immediately without any message on the screen.

I already tried some options in the (In german called "Wiederherstellungskonsole") Recovery Mode of windows server 2003 like FixBoot and FixMbr, but that doesnt help.

Trying to reinstall windows server 2003, brought me to the setup message that existing server 2003 install will be killed. that is not fine for me.

All partitions are accessible (NTFS).
I think that the problem might be the version of the ntloader, but i dont know if it is so.

Please Help me!