Hi Guys,
Providing your computer is operational, you can download (or otherwise install) Belarc Advisor, a Free Personal PC Audit Tool from...
http://www.belarc.com/free_download.html ~605Kb
No brainer/no options install. Run it to list all MAJOR CD/Product keys on your computer.
Lists all kinds of other neat stuff, hdwr config, patches, all installed software with version numbers and so on - a real handy 'must have' PC audit tool

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Outputs to your current default browser. You do not need to be online! It's not a web-based service nor reports to one - it's installed on your computer and the info is yours only and private. You can save/print the output for future reference via your browser's menus.
You can run it as many times as you like. I keep the outputs saved by date/time as I make any changes to my system - an extremely useful reference. Priceless when it comes to exploring/debugging someone else's computer.
The reason they use your browser is Belarc provides a link (an underlined *) at the end of each item for you to click to get to the install directory - very cool!
Once you know the MAJOR CD/Product keys for YOUR computer, you can install/uninstall/re-install any 'Product' via any distibution method - CD's, downloads - whatever.
There are some exceptions regards minor/tertiary installs, but run the report, then decide what these exceptions may be, and if it's of concern.
For instance, if you run Diskeeper (and you should), the registered name and key is not listed with that product in the 'Software Versions' section of the output. You must obtain this info prior to doing anything like major system re-vamps & esp b4 re-formatting your drive. Natch, you can do it the hard way as well ;-)
I've run this util on many systems, some real sick one's as well, and never had a problem. Takes about 1-2 minutes to generate the report on the everage computer.
Take note - don't get click happy with this util!