How to reset nokia 5800

After installed software or theme, then your cellphone freezed, or your cellphone restart .
How to solved this problem ?

1. Turn off your cellphone, remove your memory card
2. If the problem solved, format your memory card
3. If the problem not solved, check power switch, replace switch if needed
4. If the problem not solved reset your nokia 5800 cellphone by pressing *#7370# (ask you to entry code, standart code =12345)
5. If the problem not solved, you need to upgrade your firmware or reflashing firmware
6. Upgrade firmware/flashing firmware need tool box (like Ufs3,Mt Box, etc)
7. If the problem not solved, check your Ram/flash/memory Ic, replace if needed
8. Replacing memory IC need rebuilt imei and tuning energy managemant / PM rewrite.