BlackBerry Hard and Soft Reset

A soft reset is similar to restarting a desktop computer and is the most useful tool for resolving a variety of issues. In most cases, a soft reset will not affect user data on the device, unless the battery is very low. Also, it is a good practice to perform a sync operation before any reset to ensure that all data is backed up (assuming that synchronization is not the problem you are trying to fix).

A hard reset will return the device to original out-of-the-box condition; removing any preferences, custom settings, and third-party applications (personal information such as phone number and addresses, calendar entries, pictures... will also be erased). If possible, this data should be synchronized to a host computer prior to performing the hard reset. Do not perform a hard reset unless data has been backed up or you are willing to lose everything. After a successful hard reset, data can be restored to the device using synchronization or backup software (certain third-party applications may need to be re-installed manually). A sync backup using HotSync or ActiveSync will backup the contacts, calendar, memo's, and notes data to PalmDesktop or MS Outlook. Actual backup software can backup the entire device including third party applications.

Hard Reset
Remove and replace the battery.

Soft Reset
Hold the control key (half moon symbol under the letter "A"), the CAP key, and the DEL key at the same time.