Delete or reinstall apps
Deleting an app removes it from your phone and frees up memory. It also removes any information the app contained. So you should remove them with care.
To delete apps
On Start, flick left to the App list.
Tap and hold an app, then tap Uninstall.
When asked for confirmation, tap Yes.
To delete games
On Start, tap Games.
In Collection, tap and hold a game, and then tap Uninstall.
Xbox LIVE and Marketplace may not be available in your country or region.
If you accidentally delete an app—or ever have to replace your phone—you can reinstall apps or games you've bought without paying for them again (as long as they're still in Marketplace).
You won't be able to reinstall an app unless you have Windows Phone 7.5. If you're not sure which software version is currently installed on your phone or how to install an update, visit Update central.
To reinstall apps from your phone
On Start, tap Marketplace .
Tap Search to find the app or game you want to reinstall.
If it's a free app or game, tap Install. Otherwise, tap Buy, on the confirmation screen, you'll see a message saying you've already purchased this app. Tap Install to install it again.
Follow the instructions to reinstall the app. You might have to re-enter your Windows Live ID.
The Windows Phone Store on the web also provides a detailed purchase history, in case you've forgotten what you've bought. Phone apps and games sync directly with your phone and are not part of your media collection in the Zune software (or Windows Phone 7 Connector for Mac) on your computer.