We've all seen games where people have just slapped those ugly Default buttons into there game. They arn't even real Windows buttons because If you change your colour scheme or get XP they'll just stay the same. What makes matters worse is when the person who made the game doesn't even think about where to place the buttons and puts them in a slap-stick way all over the place.
There is no need to use the Default button EVER, even if you use the bitmap button option. You can make a far more interactive (and attractive) button with an active object for a minutes extra work.
The main thing I like about making a custom button is the fact you can add roll-over effects, this is where the button changes in some way by getting lighter or something when the mouse passes over it.
To make a button first get an active object, then make it the right size and draw a button that matches the style of your game. This should just be a still frame drawn in the Stopped animation. Then copy and paste your button to the user animation 1 section where you can make it gradually get lighter or whatever effect takes your fancy, set this to the right speed and tell it to play only once. Now you've made your button all thats left is to code it in the folllowing way:

>Mouse pointer moves over active object - set animation to 'user animation 1' + you could play a sound
>(Negate)Mouse pointer moves over active object - set animation to 'Stopped'
>User Clicks on active object - perform the task you want that button to do

And thats it, you can have animations, sounds and make your game alot more interactive and it works for EVERY type of game. And also an active object takes up only 2 blocks from your object limit, the button takes 3! So if you've run out of slots for objects, convert all your buttons now.