There are several possible reasons - nothing is ever as clear as it first seems!
If you are logged into a Google Account (like on your personal computer for example) then you will get results tailored to your search habbits. Make sure both systems are not logged into Google Accounts and repeat the search.
Different buildings using different ISPs could be routed through different infastructures and hit a slightly different geographical target, thus seeing results form a different data center.
In the SERPs, hover over any of the "cached" links for any result. Note the IP address. This is the Google Data Center where the results arew coming from.
Regarding hte desktop and laptop on the same network, is one on a DHCP and one on a Static IP? Is one going through a different proxy server, VPN or dial up connection?
Just because it is connected to a network does not mean it is using the same network rules or locations.
For example, if you are on a VPN connection with Porxy server settings to your office in New York but you searched in China the results are coming as if you were searching in New York.
Ensure everything is the same, repeat, check and analyse.
Its most probably due to one of the things I have mentioned above.
