I'm getting "ready" to do this very same upgrade path.
According to MS Knowledge Base:
http://support.microsoft.com/kb/932795/en-us
1. Make a complete backup before you start!
2. Verify the backup works!
(In case you don't have the driver support or installation just
ain't working.)
3. Wipe the installation hard drive and re-install XP (32-bit)
(I don't think you have to activate it.)
4. Boot from the 64-bit Vista DVD and select Custom Install.
(Use the same Product Key you used for 32-bit.)
Best of luck!
"Robert V" wrote:
> I have Windows Vista Ultimate upgrade which came with both 64 and 32 bit
> versions. I installed the 32 bit version over Windows XP Home. I would like
> to try the 64 bit version. Can I install the 64 bit version over the 32 bit
> version and if so how do I convert the licesene. What would be the best way
> to install the 64 bit version.
> --
> RLVaughn