Help needed in configuring triple boot on macbookpro

[arun chakrapani rao]

Hi Gurus,
I have a mackbookpro with 10.5.2 MAC OSX installed in it.
I am trying to install xp and ubuntu both on this system but in vain.
I went through the doc(Preparing to Install Ubuntu alongside OS X & Windows XP (Triple Boot) )of ubuntu in  
https://help.ubuntu.com/community/MacBookPro

both the software did get installed but when i click on windows or unbuntu in the boot option, it shows an error message saying
No bootable device -- insert boot disk and press any key.

Can anybody please let me know as to how get this solved,
What am i missing here.
I am novice in these system configuration.

Hence I would appreciate if anybody could help me out on this issue.

thanks in advance



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