XP, Ubuntu and Server 2003

Hi,

I installed XP PRO SP3 and Windows Server 2003. After that, I installed Ubuntu. Now XP and Ubuntu start normally, with no problem, but when I chose that option to start from Server 2003, I get that error message saying that the ntoskrnl.exe is missing or corrupt. Any idea how to fix that! When I unplug the Ubuntu HDD, I get the error that Ubuntu cannot load, but it is on a different HDD. One more thing, the boot.ini file on XP HDD has 2 lines for XP and Server 2003.

PS: all three OSs are on 3 different HDDs.

Thanks for your help.