I have several times.  Thats why I insist on getting the OEM CD's to restore BEFORE I have a problem.

You could look on Ebay for OEM Office 2007 professional.  Its not standard to include media for the OEM Preinstall versions of Office.   However microsoft does allow download of Office for the Retail Home and Student versions or

the Business versions.  Thats why I never get preinstall OEM anymore I always buy Retail and install myself.

This is intentional on Microsoft's part its not dell's fault.  They are restricted by microsoft to provide you with the media

if it has been more than 1 year since you purchased the product.

The trial version for Microsoft Office 2007 is no longer available. You can download a free trial of Microsoft Office 2010 instead.

Licensing Guide

OEM Pre installs DO NOT INCLUDE Media.  Unless you specifically ask for it at the time you order and pay an extra fee you do not get OFFICE media.  Microsoft specifically prohibits Dell from distribution of System Builder media for office to the end user.   When You insist on media it comes in the form of retail media with different COA Key.  Microsoft now also allows you to buy a card with Key and Download Office from their site.  Many Netbooks say this right on the box so the preinstalled Office starter can be upgraded to Home/Student or Business version by simply entering the non trial Key.

This sounds like a media version / key mismatch.

If the system was ordered from Dell with Office 2007 then you should have a Dell OEM Office CD and the required key is on the white card envelope.

This key will not work with a retail CD. Nor is it anything to do with the key on the base of the unit.

So if, for example, you recovered the install key from the original installation and are trying to re-install with a retail CD it will not work.

Or maybe the original system shipped with the 90 day trial copy of Home/Student and somebody upgraded. In that event the key was on the case for the purchased retail CD and you need a retail CD. Or the key was purchased from Microsoft.

On the assumption you have a valid Dell OEM Office 2007 Professional key but you have lost the CD, then you need to get a copy somewhere.

Well any that I have bought have had the trial version pre-installed and the CD with key with whatever version was ordered. You basically installed it yourself.

If this was a true OEM Medial Less Install then you might be able to download the software from here, if the site accepts the key. Use IE, does not seem to work with Chrome. www.microsoft.com/.../default.mspx

Thanks for your comments. In my defence:

I bought a notebook from Dell in 2007 with Office Prof 2007 installed and I also purchased the restore / installation CDs for Office when I bought the notebook. Unfortunately that notebook was a bit of a 'rogue' with around 12 major faults developing in the first six months. Due to the severity and frequency of the faults, Dell was kind enough to provide me with a completely new notebook to replace the rogue notebook, once again with software all pre-installed. As the version of Office 2007 was in theory the same on the new system as the version on the old (rogue) system, I stupidly thought the install CD's from the first system would work OK.

But no.... when I try to install Office 2007 from the old notebook using the license key from the new notebook....

"INVALID LICENSE NUMBER"

... hence the current problems.

The download worked perfectly thanks - the version of Office is 'Office Professional Hybrid 2007' and, as you said, if the key is accepted the software installs OK with that key.

Thanks again

Try this Link

www.Microsoft.com/office/backup2007