F12 installation making system won't boot

[Barry Yu]

I have a system dual boot xp with windows 7 which working fine, I installed the F12 into this system, after first part of the installation complete, and then reboot, the BIOS check finished, and the system got stuck, only the cursor kept blinking at top left and won't go further, fortunately before f12 installation I made an image of the XP which was in first partiontion of hard drive, primary active, so I used the image to recover XP and then reboot, this time the F12 can come back on and finished the 2nd half installation.
Here is my hard drive layout ;
1st partition primary active for XP.
the rest of hard drive is extended partition in following order; Windows 7, F12 /boot,F12 swap, F12 / all in ext3, and the grub was put in mbr of hard drive.
Looks like the F12 installation chaged something in primary of hard drive so it won't boot up until I used the XP image to recover it. Can someone tell me what happened? 
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