My HTC Cha Cha won't turn on, so I want to hard reset it to factory settings. Is there a possibility of losing contacts stored on the phone? (They are very important to me).
You need to differentiate between a "hard reset" (hover the mouse over that tag: a forced reboot/shutdown by removing power (take out the battery, usually)) and a "factory reset" (again, mouse-over: A factory reset results in a full reset of an Android device to the original settings of the currently-installed ROM.).
However, you can make a backup of your contacts. In the contacts app itself, when pressing the menu key, you should find a menu item for "export/import". Select to "export", and have it save the data to your SDCard. To be absolutely safe, before doing a factory reset copy all the SDCard's contents to e.g. your PC. After the factory-reset, you can use the very same item in the contacts app to re-import the data.
Btw: contacts export uses a common file format, which is understood by many other programs as well (
If you have your contacts synced with Google, they should be restored automatically once you configured your Google account on the device after the factory reset.