Why wont Winterboard work?

I jailbroke my ipod 2nd gen 4.2.1 and it went fine. i have cydia and am able to download things except it wont let me download Winterboard. Instead of the usual window that opens that tells me how much space it takes up and such, it says "the requested modifications cannot be applied due to required dependencies or conflicts that cannot be automatically found or fixed" and below it says "depends" with preferenceloader and libhide >=2.0.4 ,do i have to download these? if so how?