Well nothing, fortunately a version for Windows has just come out under the name of AirPrint Activator designed to work on both 32 and 64 bit systems (right click on My Computer Properties to discover the one you use). It’s as easy to use as on a Mac, just click a button and you’re done.
Apart from this, you need to have the latest version of iTunes installed although it doesn’t have to be open to work. For obvious reasons, you must also share the printers you want to use on the network through the Printer Control Panel. In the case of Windows 7 or Vista, it is also advisable to activate the system’s guest account, so that we don’t have to enter our user and password every time we want to print a document.