[Hampshire] Windows XP licence

I hope that this is not too off subject but the ultimate aim is to avoid
unnecessary revenue going to Microsoft which may be justifiable.

I have a customer who is about to upgrade to Windows XP pro from Win2k
and they would like my programme to be tested thoroughly on XP before
the upgrade.

The problem is I don't have XP and will have to buy it and I would like
some advice to avoid licensing pitfalls.

I can get Win XP professional OEM for about £50.00. I build my own PC's
and replace parts as necessary. It is likely that the whole machine
could be replaced in one go. I would obviously like to use this licence
forever but have heard that Microsoft don't allow you to transfer a
licence to new hardware.

The existing machine dual boots with Win2k and Ubuntu. I have also been
experimenting with VirtualBox on Ubuntu and so far it seems to be
working very well running win2k virtually. I would install XP over Win2k
and keep the dual boot but eventually it would be nice just to run XP
virtually whenever I needed to maintain the programme.

Could I do this with a single OEM license?

Thanks

Roger