Ars Technica posted a story about "Securing your Windows netbook". It included the following about the cross-platform open source Prey, which currently runs on Windows, Mac, Linux and Android:
As far as the free services are concerned, there really is only one choice out there for Windows users: Prey. Most of the other free services only support Linux or are not officially supported by anyone anymore. Prey uses tracking software that runs as a background processes on your netbook. It works by "waking up" at a specified interval, going online, and checking in with a specified Web address to verify the status of the netbook. If that Web address doesn't issue any commands to the netbook (e.g., "hey, you've been stolen, so update me on your location"), Prey then goes returns to sleep and will wake up again at the next time interval. If your netbook goes missing, you sign into the Prey website with another PC and update the status to "missing," and then you'll be able to follow the whereabouts of the system through a control panel—assuming that whoever has your netbook goes online or the software manages to connect to a Wi-Fi access point. (If your netbook isn't connected to the Internet, Prey will automatically try to connect to the nearest open Wi-Fi access point). Currently, Prey does not have the ability to 'lock' the netbook or erase the hard drive on command, so while the service proves to be a good choice to track a netbook, it doesn't offer any additional data protection.
If you want to remotely "lock" the system or destroy its data, you will have to choose a commercial service like as Lojack for Laptops from Absolute Software. The premium version of that service includes a feature called "Data Delete," which is used to remotely delete all of your personal and sensitive files from the hard drive, if you report the system stolen. Absolute Software also offers methods to contact the authorities to help track down a stolen PC, as well as monitoring what is happening with the PC. The service costs less than $40 per year and for those who travel a great deal with sensitive information on their portable PCs, the service is a real bargain.