problem in custom shaped windows forms and transparencyKey

hi dudes,
i've made a few Windows applications which i tried to have a non-rectangle form in those,so i tried to do exactly as MSDN says in Shaped Windows Forms and Controls in Visual Studio .NET.
but when i tested my application release on some destination computers which their OS was Windows XP[sp2 or 1],those areas which had the color which was the same color that had been chosen for transparencykey property of my form,are not being transparent and they are being shown to the user,and believe me that made my starting form very nasty...i tried to install the same version of the .net framework which i was developing applications with on the destinations computer,but the problem didn't solved.plzzz help me ,because i have lost a good and beautiful ability of .net if i cannot use that.i'm waiting for ur answers,and i beg u to answer me!!!
thanks alot.