If you only need to backup certain files periodically you could write a little DOS batch program to automate the process. I only need to backup my library files, (pictures, documents, etc), and a few other files like favorites and contacts. All the rest of the data on my drives needs to be reloaded from disk or installation files for the program to work properly anyway.
Here's an example of the BAT file I wrote using notepad. Whenever I need to backup I plug in the external drive and click on a shortcut to the BAT file on the desktop.
@echo off
echo Backup important files to External Hard Drive G:
pause
rmdir g:\backup /s/q
robocopy "d:\computer files" "g:\Backup\Computer Files" /s
robocopy c:\users\john\contacts g:\Backup\Contacts /s
robocopy c:\users\john\favorites g:\Backup\Favorites /s
robocopy d:\users\john\documents g:\Backup\Documents /s
robocopy d:\users\john\pictures g:\Backup\Pictures /s
robocopy d:\zips g:\Backup\Zips /s
robocopy "d:\program files\winrar" g:\Backup\WinRaR /s
echo Backup Complete
pause