Hi surabhivasu,
What you could do:
(I assume you have a single HDD with 6 partitions).
- Start computer with 1st CD of Fedora Core 3;
- When options prompt appears, type "linux rescue" (without quotes) and press "Enter".
- Confirm messages that will appear;
- After it is loaded, type (without quotes): "chroot /mnt/sysimage" and press "Enter";
- type "/sbin/grub-install /dev/hda" and press "Enter";
(Here /dev/hda is the MBR of your HDD!!)
- type "exit" to reboot and press "Enter";
Grub boot-menu should appear again
As a personal note, the last OS to be installed should be Linux (All Windowses first, then Linuxes).
Good luck and regards,
Sorin-Razvan Popa