happy singh :
i take simple back up in my external hdd while i have windows 7 in my pc. After that i install Ubuntu 10.10 and copy some files from hdd to pc. after few days i format ubuntu and install windows 7 as i connect my hdd it is showing the space of data but no folder is showing in hdd. Please help me
Ubuntu should not have messed with your external except to add a trash bin (hidden). Try and see if your folder is hidden for some reason by going to folder preferences in windows and click show all. I have seen viruses that mask files and folders from windows, did you connect your hdd to a windows computer that may have been infected? If you have the space on the hdd, boot to your Ubuntu cd/USB and make a copy of the desired folder onto the hdd or to your internal hdd and see if that doesn't fix you up.
BTW, any reason you were using a 3 year old version of Ubuntu rather than a newer one? More and more compatibility issues get cleared up with each release.