yes my hard drive had a 100 gb primary partition for FAT32 which i thought of keeping for later installing windows, and two more 30 gb each partition both NTFS.After that i had the root,boot and swap partitions for linux.I think the problem may have come coz the initial cylinders had FAT partition and grub may not have been loaded in the mbr part, this is what i could guess. The acer laptop is a new one just 3 months old, it has a 320 gb sata hdd and a intel i5 processor with 3gb ddr III ram.I wanted it to be a dual boot but i am fine with linux also as long as it works fine.So,last night i tried re-installing this time i removed all the ntfs partitions and the df output i am pasting here:-
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda2 305339656 6344932 283484352 3% /
devtmpfs 1374872 260 1374612 1% /dev
tmpfs 1376312 424 1375888 1% /dev/shm
/dev/sda1 247919 26416 208703 12% /boot
i gave 250mb as boot 2gb-swap 250gb-root rite now i am online using the same laptop
so i am keeping my fingers crossed,hoping this time everything works fine.
@bigrigdriver i would like to tell you that i didnt made any such changes in the bios.
@gd2shoe dvd drive is working fine
anyways thanks to all, i guess i have to download a lot of other drivers like for my wi-fi,nvidia video card and webcam.