Can I do this

[RunAway]

This may be a dumb question but I have an old Dell that Im fixing to scrap and just wanted to make sure I could use the Windows key code from the Dell on a new ATX machine...

 

[wilsoncd35]

You likely cannot. Not legally at least. It is likely original equipment manufacturer (OEM) licensing and cannot be transferred to another computer. Some good reading on OEM and Windows at the URL below. good luck.
http://www.tek-tips.com/faqs.cfm?fid=4004

 

[douche]

Unless the licensing was for more than 1 PC, than legally, NO.