paint bucket/fill, prob

Hi all,
im quite new to PS im using PS CS. now whats happening is i have selected a circular area with the marquee tool on a transparent background and i want to fill that area with colour, using the paintbucket tool i attempt to fill area but what happens when i do this is it acts like a spray can does, dark colour in the centre fading aways towards the edges also it does not actually fill the selected area it's as if i have not selected it, but i have.
I realize its probably something i am doing wrong and is bound to be something simple but i just cant figure it out, i have searched this forum for simular probs but cant find none so please help

When you click and draw a marquee, check the options bar (below the menu bar and which usually changes depending upon the tool you've selected) and see if the feather text box is set to something, if so set it to 0, if you can't find it you also try pressing Ctrl+Alt + D to display the feather dialog box and see if it is set to something also

if this does not solve it, just tell me

Excellent thats solved the prob, it was that pesky feather thing all the time.
thank you so much for your help