For those video/audio/3d/emails/webpages/pdf files your best bet is to copy them across manually folder by folder, if they won't go all at once go by copying them sub-folder by sub-folder. Right click on the files and "send to" your external HDD. Then in future at the end of each day plug in the external drive and copy onto it all the new files you've made or edited than day.
Can you give more details about these "locked files" and "running out of space", is this because you are trying to copy your whole hard-drive ( all of C:\ ), which doesn't all need copying, only your personal files and folders need copying. Another issue you might have is the formatting of the external HDD, if it's set up in fat32 format then you won't be able to copy onto it any INDIVIDUAL file larger than 4GB, you can reformat the external drive to NTFS to get around this. Make sure that any data currently stored on that external drive is backed up somewhere else befpre you format it.
Alongside backing up your files backing up your system is also very important, this is called making a system image, windows has internal tools for this under "windows 7 file recovery" or "file history" in control panel. This can als be done with macrium, which provides a free program for making system images. You should make a few system images but you don't need to keep making them regularly, you can just keep a few old and good ones. When you need to backup new files, or altered files, don't use a system image, just copy those inidividual files manually.
Manual copying to external media is the easieast way to backup files, Whereas a system image backs up the whole state of your computer (all your installed programs, your operating system settings, the settings of all your instaled programs...) as a snapshot in time you can return to in case of disaters. A system image is a bit like a disc with which to reinstall your OS, only a system image reinstalls the OS in the configuratiion you like it, with all your programs installed, rather than in the default configuration with no programs.
Edited by rp88, 20 September 2015 - 11:47 AM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB