simpleplanfan

ok so I got Sims2 for my birthday and wanted to play it. I tried to install it and it said I needed to install DirectX 9.0. So I went to microsoft.com and downloaded it on my computer. When it got to the part to install it, it wouldnt let me!! A message came up that said " A cabinet file necessary for installation cannot be trusted". WHAT DOES THAT MEAN AND HOW DO I FIX IT??? Someone please help me!