Upgrade from old Dell XP machine to new Windows 7 Machine

I am building a new office machine which I would like to stick windows 7 onto. I also have an old Dell which came with windows XP on it. Can I use the XP key from that in order to use the windows 7 upgrade version?

You cannot use the key with the upgrade. You have to actually allow 7 to see the XP installation first. Then you do a custom install (clean). Just finally upgraded myself.
There are soem other work arounds for this. Just google it.

OEM licenses do not allow you to transfer to install to a new machine. I'm not going to dig up details, but I doubt that the license for the upgrade is going to let you 'upgrade' from the OEM install on a separate machine.

You might technically be able to get away with it but I wouldn't risk it for a business. Just go buy a new license - it's a tax write off anyways.

Ok thats what I was thinking, but i couldnt find a concrete answer anywhere, so thanks for clearing things up.

The best thing is for you to try. I actually read that you can do a clean install with the upgrade disk.