If you are facing any difficulties in following the manual procedure to enable AirPrint service on Windows, now you can install AirPrint service through AirPrint installer (by TadGhostal) which is compatible with Windows 7, Windows XP and Windows Vista. For those who don't know, iOS 4.2.1 comes with a unique feature called AirPrint which allows you to print your documents, emails, web-pages and photos over a Wifi connection with your Apple iOS device.
Prerequisites:
- Download and install iTunes 10.1 from here
- Make sure the printer is setup as a shared printer on your local PC
- Printer and iOS device should share the same Wifi connection
- Make sure you have full administrator privileges to enable / disable services on your PC
Procedure:
Download AirPrint installer for Windows from here. Once downloaded, right-click on setup.exe and choose Run as administrator from the pop-up menu.

Just follow the on-screen instructions to install AirPrint service on Windows:








Once installation completes, Windows Firewall will prompt you allow or deny AirPrint features to be shared over networks. Click on Allow access button.

Please note that only HP ePrint enabled Photosmart, Officejet and Laserjet printers currently supports Apple's AirPrint service. You don't need any additional network setup if you are using one of these printers and can print any media directly from your iOS 4.2.1 AirPrint enabled iDevice. [All the credit to this installer goes to TadGhostal @tadghostal]
Update: The AirPrint installer doesn't work on the iOS 5. You may try FingerPrint by Collobos instead if your device is running iOS 5 or higher.



