Holding cursor in vertical or horizontal mode

My Mac friends tell me that I can use a keystroke to lock the cursor in such as eraser mode so it will only travel in a horizontal or vertical mode as long as the key is held down. I don't find it listed in the Photoshop 7 Keyboard Shortcuts that I downloaded from the FAQ Archives. Is this feature available in Photoshop Version 7.0 running on a Compaq Presario SR5030NX? OS is XP Pro, Service Pack 1. Thank you for your help, It is appreciated. Ron

Hold down the shift key while moving the cursor.

This constraining action by the Shift key (Normally to 45° increments) is a pretty universal feature and not a Photoshop short cut.