you can download the full slipsteam version of MOSS 2007 with SP1 here:
Office SharePoint Server 2007 with SP1 (32 bit)
http://www.microsoft.com/downloads/details.aspx?FamilyId=2E6E5A9C-EBF6-4F7F-8467-F4DE6BD6B831&displaylang=en
Office SharePoint Server 2007 with SP1 (64 bit)
http://www.microsoft.com/downloads/details.aspx?FamilyId=3015FDE4-85F6-4CBC-812D-55701FBFB563&displaylang=en
Download the OfficeServerwithSp1.exe executable
This will work with the tiral and full product keys