Need to copy your Outlook signatures from one computer to another? Just copy the contents of this folder:
That %appdata% code will expand to the correct name for XP, Vista, or Windows 7.
Another way to get to that folder from Outlook is to go to Options > Mail Format Ctrl-click on the Signature button. That’s explained in more detail here.
This even works copying signatures from Outlook 2007 to 2010.