I recently reformatted 2 of my friends computers and installed Windows 7 Ultimate 64 bit - the version I have been using for years. It is build 7600 so it is compatible with the loader. My friend I am helping right now has a custom built computer. The mobo is a GIGABYTE GA-73PVM-s2h. I went and changed the profile to both gigabyte, but what then? I tried custom serial and acer serial, neither worked.