At a guess your External drive is formatted in FAT32 and so cannot use files over 4G.
Convert it to NTFS
the only real reason for sticking with the FAT32 file system for any of your data is if you have more than one operating system on your PC and the other OS's can only see FAT32 partitions (as would be the case with Windows 98, for example, which is incapable of reading NTFS data).
To convert your drives to NTFS: Right click on 'my computer' and select 'manage' From the computer management window, expand storage and select 'disk management.' Using the 'file system' column of the upper pane of this window, you can easily check what file system each of your logical drives is using. Make a note of this information. Now open a command prompt window by going to 'start\run' and typing 'cmd' To convert a disk to NTFS, type 'convert (drive letter): /fs:ntfs' So for example, if you were going to convert your C: drive, you would type 'Convert c: /fs:ntfs' at the prompt.
Hi again, i googled the question above and now realise that it wont make any difference to the data on the hd. However, i followed instructions, restarted the computer and external hd but under properties on the hd it still says 'Fat32'!! Grrr! Please has anyone any ideas?