Finally got the problem solved. Although its not quite clear as to what solved it, i did the following after frustrating search and thought:
1)the partition table was obviously altered and hence /etc/fstab had invalid entries reflecting the old structure. =>Removed unwanted entries and tried to make the file a minimal one.
2)By trial and error guessed what could be the root partition number .....found it to be /dev/hda6 and not /dev/hda5 as it was earlier.By keeping this as a reference changed other partition device name entries and rebooted.
3)Bingo! fdisk -l at last gave an output. But i don't understand this. does fdisk read the fstab file for any querying?.....so brushing aside such doubts I issued
grub-install --recheck /dev/hda
this gave a different error this time stating the file
/boot/grub/stage1 not read correctly
4)Then I had to painstakingly study the
pages and learnt how to install it natively. I think it was easy at the end and I did learn a lot.Thank God I had this problem or else I would'nt have learnt so much.
5)But no, the problems were not yet over. The native install method just gave me a grub prompt from where I could enter commands everytime I wanted to boot. This was ok with me but thinking of my father I badly wanted the menu interface....and then further research(?!!) gave me the perfect answer
install /grub/stage1 (hd0) /grub/stage p /grub/menu.lst
Hope this thing helps someone with a near-similiar problem.