I am going to do a clean install of Windows 7 32-bit on a new internal hdd on my Inspiron 9400. There are several choices: Professional SP1 OEM system builder for refurbished PC, Pro SP1 needing activation by phone, Home Premium SP1 OEM System Builder New Packaging, & Home Premium SP1 OEM System Builder for Refurbished PC. What is the difference between the DVD for new installation and for a refurbished PC? And which one is recommended for the planned free upgrade to Windows 10?