i transfered some data into my external hard drive nd i just unplugged it from my friend's comp "win 8" and nw when m trying to access those files they r not shown in the hard drive when i plugged it in in my comp m using windows 7 ultimate x64.
More about :extracting file issues external hard drive
you *NEVER* just unplug an external drive. You should always use the operating systems 'eject' or 'Safely remove' feature.
You have either corrupted the file system or caused actual physical damage to the drive. please run disk error checking (with both options enable) on the drive. You can find it by right clicking ont he drive and selecting properties from Explorer. Error checking can be found on the Tools tab.