Beg, borrow, or
steal buy a pair of good binoculars and take a close look at it, the next time you have a clear night.
Note where it is in relation to the moon and/or stars, and make a visit to http://www.heavens-above.com. Give it your location, and ask for a full-sky map for the date and time in question.
How long does it take stars or the moon to cross your window? What time does the mystery light set?
Based on the brightness, I'd say either Jupiter or Venus. Even airplanes aren't that regular, and they don't move that slow. However...
Neither is in the night sky right now. Mars and Saturn are, but they are pretty undistinguished right now. The only other bright light I can think of is Sirius.
"For shame, gentlemen, pack your evidence a little better against another time."
-- John Dryden, "The Vindication of The Duke of Guise" 1684