Suppose I've install a 32-bit version of Vista on my machine and activated it. I now want to switch to a 64-bits version of the same OS. In this case, do
I have to pay for a new license or can I reuse the old one?
Anyone possessing an official licensed version of Windows Vista 32bit (Family Premium, Pro or Ultimate) can ask Microsoft for the 64 bit installation DVD.
You won't have to buy another licencse, but still you'll need to pay for the shipping of the DVD.