I just got done building my computer and was installing Win 7. I was able to obtain a product key from my school and used my friends Win 7 cd. I choose custom install and it recognized my hd. Then I entered my product key and it wasn't working. I later find out that he gave me his Win 7 Ultimate cd and I have the product key for Win 7 Pro. I then was able to get a Win 7 Pro cd from another friend and went through the same process. This time when I get prompt and choose custom, it does not recognize my hd anymore. Can anyone help me as to why this is occurring? TIA