Hi
Assuming your Dell had Windows 7 not Vista when new
(and you are not trying to upgrade the Windows 7 version from Home to Ulimate)
Dell will sell you a new recovery DVD which does not need a product key but only works on Inspron n5010 models
You would have the option to run the recovery disk builder program while Windows 7 is working, (there are usually reminders).
(read the user guide, usually installed on your PC or available from Dell website on how to do this)
regards
Mike Barnes