vista upgrading from basic to ultimate

hey guy bling here so i have vista basic 32 bit right now and i have got an ultimate disk as a present now i would love to upgrade from basic to ultimate but the problem is that the ultimate is not an upgrade disk but the full thing and when i go to install ultimate usually we have the option of upgading or a fresh install i prefer upgrading because i have some importnant files but the upgrade is greyed saying that i need a newer version of windows weird aint it so if anyone has upgraded by this method pls pls tell me how i would love to have ultimate instead of boring basic

You SHOULD be able to simply modify your product key to enable the features of Ultimate. The features of Ultimate are included on the basic version as well, but disabled based on product key.

1. Click Start, right click Computer and click Properties
2. Go to the bottom of the window, and click Change Product Key.
3. If a UAC prompt comes up, click Allow or enter in your Admin password.
4. Change your product key to the Vista Ultimate product key.
5. Do as it tells you to.