Vista OEM 32-bit Key with 64-bit OEM?

[IMJ]

Hi, I did a search about this but wasn't able to find a clear, definitive answer.

I currently have a Core2 Duo processor but in the interests of avoiding early hardware and software problems I opted for the 32-bit OEM version of Vista Home Premium. Now, if I borrowed a copy of the 64-bit OEM version in the future, would I be able to use my existing (32-bit) key when I reinstall it on my computer?

I have a friend who's considering buying Vista but also is not sure about which version to get, so ideally he could get the 64-bit version, and temporarily borrow my 32-bit disc, and then later I do the reverse. From what I understand, the licence keys will work for either version, BUT it's not clear whether once you've chosen one, if you can change it over to the other version later. Or does the key "lock" to the 32-bit or 64-bit version once it has been used for the first time?

Thanks in advance!

[redddraggon]

The key is just "locked" to your motherboard once installed and it is only linked to which version of windows, ie Home premium or ultimate etc, not 32/64 bit.