Identify if stolen

Does the seller have the original invoice for the system?  If so, it's more than likely legit.  If not, being as how it's under warranty until 2006, he may not be the original owner.  Since the original owner is required to effect the warranty transfer to a new owner (you), and since there are no exceptions to this policy, if the seller can't produce the proper paperwork showing that it was sold to him/her, you'd probably be wise to take a pass on it.  If it is stolen, and if the original owner reported same to the authorities, you'll be unable to get any service for it - aside from any personal problems you might have with receiving stolen property.

Occasionally, a local police department will check for stolen status on articles of this type, if you provide them with the serial number (or in this case, the Service Tag ID).  You might also try posting this in the Customer Care - General conference.  Perhaps a moderator there can see where the notebook stands in their records.

The bottom line is that if a deal seems to be too good to be true, it usually is.  You can substitute "legitimate," "honest," or any other similar word for "true" as you see fit.

Make the sale contingent upon sucessful transfer of the ownership/warranty to you.  The seller will have to initiate the transfer by calling Dell directly.  If he is sucessfull you are home free...

In the US, you can have the owner transfer ownership to you online.