Ok, I have no concerns about the disk being genuine, nor does microsoft, the only issue was the serial number. Do you know anything about the build numbers, are they different if from Dell or OEM. My build is 7601.
Well, go ahead and try to activte with the new serial #.
As far as I know, every windows 7 dvd is exacrly the same, except for the 32 and 64 bit variants.
Each contains all the different versions, as well as the oem, uptate, and retail versions.
When you install, you identify the type of windows, home, ultimate, update, etc, and when you activate, the legitimacy and appropriateness is checked.
So, you should be ok with a legitimate code.