Where did you save the .dot template for your letterhead? You need to save it to the Templates directory of your computer to use the letterhead template you created.

On my computer the path to my MS Office templates is

C:\Documents and Settings\jdoe\Application Data\Microsoft\Templates

Place the template in that directory and when you go File>New from the menu in Word

Then Choose Templates on my Computer to select your template to use, this appears in the right column of my word document on my computer, It may be different on yours.

And select the template and begin using your letterhead.

Good Luck!
R