This excerpt taken from the HPQ DEF 14A filed Jan 29, 2008.
From Logan International Airport and Route 1A South:
Follow the signs towards I-90 WestTed Williams Tunnel. Take the Ted Williams Tunnel to Exit 25. At the top of the ramp proceed straight onto B Street. Follow B Street to the end and take a right onto Seaport Boulevard. The Seaport Boulevard entrance to the Seaport Garage will be on your right.