Problems printing with photoshop.

Hello I'm using Photoshop C2.. and I've been having problems printing.. I need to print in a letter sheet an image.. the image should be printed enterily on the letter sheet.. but even when I select my document size as letter, then I print it using a hp deskjet 990c and a laserjet one 2500... the print is not covering the entire sheet like it supposes to... what am I'm doing wrong?.. can somebody help?.. thanks in advance.

Serg