If you encounter situation like below on your 6600,
1. Blank screen phone unable to reboot.
2. Phone only able to boot-up to "Nokia" word screen.
3. Install some program but not able to uninstall it after that.
4. Error messages such as "Child Installer" keeps popping-up.

Do a Full phone formatting on your 6600! as steps below,

1. Make sure you have at least 3/4 charge of battery power left.

2. Backup your contacts list and personal files to MMC memory card.

3. Switch-off your 6600 phone.

4. Press and hold 3 keys;

Green dial key, * (star key) & no. 3 key and then press the power on/off to swtich on the 6600 phone.

Remember, do not let go all of the keys and hold keys until you see a formatting word screen show!

5. After a few minutes when the Full phone formatting completed, your 6600 will back to original system and factory settting.

All apps installed & not of the phones' default will be lost. If you did a backup on your mmc, you can restore it back to the C drive again.

I Hope May Be Works With All Devices