As Dell-Jesse has already said, "The COA on the back of the system is ONLY for the Vista Home 32 and 64 bit and NOT Vista Ultimate or Business. Dell computers will not need a COA provided you are using the Dell Supplied DVD on a Dell Computer. The bios detects that it is a Dell Disc and a Dell System and will not ask for a COA". Good luck with the new OS!
Mine had the Vista Express Upgrade using the Dell's Express upgrade DVD for Vista Home Premium 32 bit in March 2007.[from XP to Vista was a promotion at that time]. I did a clean install of the vista Home Premium 32 bit using the upgrade DVD at that time. Now I have obtained from Dell VISTA 64bit Reinstallation DVD[Dell Rep told me that she did not have the Vista Home Premium 64 bit and is it ok for me to receive the Vista Ultimate 64 bit reinstallation DVD-for which I agreed] The Reinstallation 64 bit Ultimate DVD has arrived today in an envelop. I do not find a certificate of Authenticity[COA] inside. However the sleeve that has the following written on it:  "The Microsoft operating system Certificate of Authenticity [COA] is a multicolored label located on the side or bottom of your computer. The COA contains the product key code, which might be required to complete the operating system setup." Now where do I stand? Can I go ahead with my clean install of the Vista Ultimate 64 bit with the Disc I just received after formating my Drive where my present Vista Home Premium 32 bit is present.  I own a single computer in Home environment. Snow
Will the COA for my VISTA Home Premium 32 bit[oem] work for VISTA Ultimate OEM 
disc form Dell.