Thanks for you reply Radenight,
I have tried easyBCD before but unfortunately does not help in this case.
easyBCD can't detect xp partition initially so I had to manualy add xp entry into mbr.
And again, after I restart, I still can't acess os selction screen unless the install disk is in dvd drive
If I put install disk into dvd drive, I'm now able to go to os selection screen (which was created by easyBCD from windows 7)
I wonder if there is something I can do with xp boot.ini to fix this ?
Thanks