CookieMonster - do you mean the size that i make them at?!
When you open Adobe if a new window hasn't popped up yet to see what you'd like to do
just click
File>
NewThen another window will pop up. below preset sizes you will see numbers, and beside those numbers you will usually see CM, PIXELS, PERCENT, COLUMNS, MM, INCHES, POINTS AND PICAS.
i ALWYAS work will pixels unless its a full page of something.
so click
pixels for the first two boxes in drop down. and for the third box click
pixels/inch and make sure for icons that your resolution is set at 72. the smaller the image you don't need a higher resolution. but as you get bigger you may want to increase that. 72 is generally the default for icons
now for the number part. just erase the numbers that are written and type in 100 for both boxes.
and click okay.

and there you have it, you can now make 100x100 icons

I have some more icons to post, i just have to upload them!!!