Microsoft has released a free program called Mouse Without Borders that lets you use your mouse and keyboard to control up to four PCs across your network.
Not only that, but files can also be dragged and dropped between PCs, the clipboard can be used across all of them, and you can even lock all your Windows PCs simultaneously.
The software came out of Microsoft's after-hours project group, "The Garage", from developer Truong Do, who reportedly couldn't find the tool he needed to do the job, and so he built one.
We guess he didn't look particularly hard, but the extra options and friendlier GUI are rather appreciated.
If it sounds like Mouse Without Borders will fit your needs, you can download it here.