hi guys!
i am trying to create an mp3 player using fasm, any idea how i could create a gui interface as nullsoft has done for winamp.
Any tutorial about gui programming using fasm?

GUI programming in FASM is basically same as GUI programming in C. So you can (have to, in fact) look for C GUI programming tutorials.

Don't miss the free audio codecs Vorbis, FLAC and WAVPACK

I don't remember where I got this from.
It's a CD player and it's in MASM but it may still be useful.

If you mean a skin, I think you should look at all the functions regarding the creation of regions with winapi. They use bmp, as far as I know (very little, at this moment, as they are not in one of my projects at the moment), with one colour set as transparent.

Skinning a window is quite easy, and there is no need to try and understand winamp sources when there are a number of demos and tuts available on the web.

u mean forgers-win32-tutorial.zip?

Look into GDI+.

ive found this site

http://msdn.microsoft.com/en-us/library/ms645434(VS.85).aspx

Ok, here's my idea (ignoring the fact that you just found the CreateDialog function and seem pretty satisfied about it =)) ) :

* create a popup window (or dialog if you want) without any decorations
* create some bitmaps:
- one hotspot bitmap used to identify hot spots (clickable areas) inside your UI;
- one appearance bitmap containing default images for each area you defined in the hotspot bitmap plus the background of your skin (this would also be a hotspot with say clor #000000 in the hotspot bitmap - in case you want to make it draggable);
- add bitmaps for the following states of the clickable areas: focused (if you also use keyboard navigation), hovered, pressed, disabled etc.; these are the basic states of a button control, but you can add as many as you wish - you can also add multiple images for just one state to create an animated effect (e.g., when hovering the mouse, "fade to green" effect - which would be created by multiple bitmaps with different shades of green)
* implement mouse (and keyboard) actions - use the hotspot bitmap to hit-test for an area then perform an action based on the color in that area and the state of the mouse buttons / position of the mouse etc.

This way you could allow for easy editing of skins (no INI files, no configuration of any kind - just bitmaps). I would not use regions unless I were writing for win 95 !?
While I did say "bitmaps", I'd probably go with transparent PNGs loaded and drawn via GDI+ (there are GDI+ APIs you can use for this) and I'd use a per-pixel alpha-blended layered window.

If you don't understand anything I just said, start googling!