Please Help On Modding A Bit

Please Help!! I am modding my login screen.. i tried to cut the login box.. but it just cutted and there is some part white.. like i cut it then it look like a square.. there is no corner from top right and left.. but when i paste it it is white .. i want it to be nothing..

i search on google.. and it is exclaty what i want.. Google

but i tried to make the login box same as normal and it come out like this..
i guess u dont understand so here is the screen shot..
http://img812.imageshack.us/img812/5167/26103131.png

i cut the login box so fxcking carefully and then i paste it and it have the white part.. how the hell i remove it.. like this ..