They use Volume License Product where M$ Sell you 1 Install Disc & Product Key and then Authorize you to install this onto X number of systems. The X Number is the Number of Licenses that you buy starting with a Minimum of 5 and working up to however many you need.
If you are using OEM product from Dell they will have different Product Keys and besides costing more than Volume License Product they also make it harder for the People/Person doing the roll out as Under the License Agreement you should not Bulk Load the different Systems but Individually Install each computer.
However provided that you are extremely careful and [b]Do Not[/b] miss any you can Bulk Load all of the Systems and then alter the Product Keys to what they should be with for Windows and Office something like Key Finder from Magical Jellybean
http://magicaljellybean.com/keyfinder/
This allows you to individually alter the Product Keys on each system but within certain Limits. You can not use a different version of either Office or Windows and use the Product Key. So if you have Vista Business OEM you [b]Can Not[/b] use a Vista Business OEM Product Key. The same applies to Office as well. ;)
Now for the warning. While Bulk Loading is frowned upon by M$ it is doable provided that you [b]Do Not[/b] Miss any systems. If M$ was to perform a Software Audit on the Business and finds more than 1 System using the same Product Key they can quite rightly Hit the Business with a Fine for Pirating their Software. Doesn't matter if you have the correct number of Licenses you [b]Can Not[/b] have more than 1 system with Unique Product Keys. If you do they will Hit the Business with a $250,000.00 Fine and list the Business and it's Principles on their Enforcement Alerts on both their Web Site and printed material. This includes the Principals Home Addresses not just the Business Address. They will also tie the company up for at least 18 months in Legals which will be good for about the same cost as the fine so for a [b]First Offense[/b] expect to be out of Pocket for at least .5 Million.
Naturally if it isn't the first offense the Penalties from M$ will be larger and I should say [b]Considerably Larger.[/b] If you are at all worried you should install this software individually particularly if the company has been hit for M$ Piracy Previously. ;)
Col