Before reset the Samsung I5500, Copy all your necessary data, Contacts, Messages etc. otherwise your Data including contacts, messages etc. will be lost. If possible back-up the Data to your computer using Samsung KIES. If your Mobile freezes or hangs then just reset the Mobile to function properly. To reset follow the below instruction.
Samsung I5500 Galaxy Android Mobile Factory Data Reset or Hard Reset
Settings ->Privacy ->Factory data reset ->Reset phone->Erase everything
When the device is turned off, Press and hold VOLUME UP + DOWN + POWER ON the phone, When an exclamation mark appears then select HOME key(Note: The Mobile should be fully Charged)