Uhm not really can help over the forums, as this would be something you want someone next you IN PERSON assisting because we can't see what computer it is, do you have Hard Drives installed, are the harddrives wiped first, are they plugged in properly and show in BIOS (if you don't know what that is just stop now and seek a professional, computer friend, take to mom and pop IT store), why are you installing Windows 7, was there a previous OS on this PC, is this a PC your installing on, what PC is it, what are its specs, etc. etc. etc.
Just posting a anonymous vague question just wont' help us help you.