What do you want to backup your hard drive for? Are you planning on installing W7 and don't want to lose personal data etc? There are many ways to go about this. More details would be a big help, like current/planned OS, reason for backup, what exactly you want to backup etc
its just dat d windows7 installation sez all d data from ur hard drive will be deleted during installation.....i knw dat only c:\ drive is deleted during windows xp installation...does the same also happen for windows7 (d documentation is confusing)or d entire hard disk is formatted(dat is all d partitions)?