Strange problem in Ubuntu installation

[Amrit Pal Pathak]

i had installed xp.Then i installed the ubuntu-10.04 inside the
xp(Wubi).Everything went fine.After ubuntu's installation i rebooted
the system but i couldn't get the option to select the OS of my
choice.Windows xp automatically got started.
Why?
I had done it already number of times but never got such a strange issue.
Please somebody help me to find the issue and how to fix it.

-- 
Thanks
Regards
Amrit Pal
amritpalpathak.blogspot.com