I am wondering where I get the 25 character product key that I need for this computer.

Hi,
If you have purchased the "windows vista cd" operating system separately then you will find the product key on the cover of the cd itself. If the "windows vista cd" came with the system then also it would be on the cover of the cd. Sometimes the cd is provided at the point of sale, so you can contact the manufacturer of the computer they will provide you the "windows vista cd" with the product key.
If this doesn't work then the last option is to contact microsoft on (800) 426-9400, they may be able to help you out.
Hope It Helps
If your able to login into your system, please let me know then I'll let you know how to extract the key from your computer itself.
Thanks and Regards
Anand Sachan