vista home premium to vista ultimate

I have a new desktop which came with vista home premium. I have purchased vista ultimate separately. Can I upgrade it to ultimate without uninstalling the existing vista?

YES. People ask that alot, but its ok. Yes you can, just put in the disk, and either boot into it, or just open it, and click install. The "Upgrade" selection should be available, and you can install it that way. I would recommend (as does the installer) that you have a backup of all your data just in case it does delete something. It should work just fine, though you may lose somefiles, it will only be few at worst. have at it and let us know how it works.

~Lordbob