DirectX Help Please

I downloaded the very newest version of DirectX For Windows 98 (version 8.1) and it downloaded fine and everything, BUT, it wont work. I dont know why, but the sysdiag command or whatever dosent work which makes me think that my computer isnt recognizing it and the games i want to run arent recognizing. I have uninstalled and reinstalled several times, all with no luck. Does anybody know what the deal is?