Ok – this looks like a fun one (And yes, I do have a strange idea of fun – profesionally speaking).
1) From a Command prompt enter “ipconfig /all” and verify if the DNS server is, in fact, the correct one. Since you said that this is a laptop, it may have been configured manually for outside settings. This can also be verified by use of the nslookup command to see what default DNS server it is set to use.
2) You mentioned that the system could ping outside IP addresses, but when you mentioned URLs, didn’t specify whether or not these were bare DNS names (like www.yahoo.com) which makes use of the resolver (DNS Client) software.
3) Have you checked this system fully for spyware? This should also include whether or not the hosts file has been modified. (C:WINDOWSsystem32driversetchosts on XP).
Let us know what you find – follow up is ALWAYS appreciated.
Bob (The world would be better with more of us, right Bob?)