Help cutting a start menu

Ok...I've walked back and forth thru Vampothika's tutorial (very well done, btw) and I CAN'T CUT THE START MENU CORRECTLY. I've tried every method I know, and it always stretches the pieces, or shortchanges them, leaving them oddly distorted, or with discernible lines. While admittedly, I am NOT in any way a GIMP master, I DO know how to cut things, whether its shapes, images, or even boxes. It's a very simple start menu image, and I would appreciate any and all help. I'm going wonkers over here =(

I've inserted the .png file. mebbe someone would be nice enuf to cut it =D

Anyways, again, my thanks, in advance, for any/all help/advice/criticism/stones/farts in my general direction, that anyone would care to give~