It isn't as difficult as you might think, especially with Vista or Windows 7.
- In Windows Explorer, highlight one or more files.
- Hold down the shift key, and right-click on any of the highlighted files.
- When the context menu pops up, left click on the Copy As Path entry that has magically appeared because you're holding the shift key down.
- Now it is saved in the "Clipboard" and you can use CTRL/V to paste it to the program of your choice.