I have a mid 2007 13" MB 2GHz processor and 1 GHz ram that I purchased a new HDD for. I purchased a Seagate momentus 320 gig drive and when I have it installed the os will not install. I am trying to install a retail version of 10.4 but would rather install a copy of 10.5 but at the moment do not have a copy at my disposal. Any ideas anyone?