There are thousands of apps in Apple's iTunes app store that bring extra functionality to the iPhone. But unlike handsets that run Google's Android open-source platform which allows users to download apps from third-party stores, Apple smartphones owners can only install software available through the app store and approved by Apple.

However, if you 'jailbreak' your smartphone you can run and install third-party apps not available from the iTunes app store. 'Jailbreaking' simply mean installing a program that removes restrictions in the default software so you can run other apps.

Although it's worth noting, jailbreaking your handset does run a small risk of bricking your phone, rendering it unusable. So think carefully before you go ahead with this and don't say we didn't warn you. Furthermore, it will void the warranty on the Apple smartphone and there's no guarentee the apps you download haven't been infected with malware, as has been the case for some Google Android apps.

Also, remember to back-up your handset in iTunes so that if any problems occur you can restore the iPhone to its original state.

We've already shown you how to jailbreak an iPhone running iOS 4.3.3 or below. However the vulnerability that this method exploits was patched in the iOS 4.3.4 software update, so if you're running this or the latest version (currently iOS 4.3.5) then you'll have to use a different process. It's also worth noting if you jailbreak it this way, every time your device runs out of power, you'll need to open Redsn0w, select the iOS 4.3.4 firmware file and then repeat step three listed below but instead of checking Install Cydia, just select Just boot tethered right now. Then connect your device to your PC and press Next.

Here's how to jailbreak iPhones with iOS 4.3.4 and above.

Step one
You'll need to start by downloading both the iOS 4.3.5 and iOS 4.3.4 firmware files to your PC from Apple, as well as running the latest version of iTunes.

Step two
Now download Redsn0w 0.9.8b4. Open the software and you'll be asked to select an iOS firmware file. Choose iOS 4.3.4.

Step three
Once the firmware has been recognise, press Next. Now check the box next to Install Cydia and select Next again.

Step four
You'll be asked to plug your iPhone into the PC and then turn it off. Press Next.

Step five
Now, you'll be instructed to put your iPhone in DFU mode by holding down the Power and Home button for various periods of time. Follow the on-screen instructions as there are a number of ways to do this depending upon the device. Press Next

Step six
The jailbreak will now begin. While this is happening, it's recommended you don't use your PC.

Step seven
When the jailbreak has finished, select the Cydia app from the Home screen. You're now free to browse and install whatever third-party apps you want.