making perfect circles

I am making buttons for a promotion and need to know how to make a perfect 2" circle i can use as a template for my design.
Dont laugh :p

select the circle selection tool... drag some guides out from your rulers. Put one at 0". And another at 2". Do that horizontally and vertically. Now hold shift and click and drag from one corner to the other.

Open your image, select Ellipitical Marquee Tool. For Style, select Fixed Size. Type in your dimensions, be sure to put in if you are using inches, or use px for pixels. Good Luck!