Regarding download for mine prepaid card

I downloaded Minecraft 1.5.2 prepaid card on this computer but i didnt play for a while and when i went to use it it wouldnt download so i tried redownloading it through minecraft.net but it still would not even run on this computer and I dont understand why or even if there is an issue ...i also had magic launcher 1.0 and several mods on it . Would appreciate any help resolving this issue