This guide will describe how to flash your mobile phone and the software required for it.
Software required:
Z500 & Z300 firmware downloader (MultiLoader v1.6): Download
Z500 firmware BVEG4_EG5: Download
USB drivers: Download
Before you start it is recommended that you take backup of your settings, phonebook, smses, etc, etc. When the flashing is done the phone WILL erase itself.
Firmware version legend:
Z500BVEG4
Z500 = model
BV = Operator
E = 2005 (F = 2006, G = 2007 etc)
G = Juli (H = August etc)
4 = revision (note that G4 in one region does not have to equal G4 in another)
Now to keep it short close down all programs that you can including the ones next to the clock. Especially antivirus programs etc.
Connect the phone througt USB and install the drivers. Disconnect it.
Take out your simcard. While the phone is powered down press and hold key 9 and then start the phone. The main screen should be white and the small should say DOWNLOAD with red background.
Unpack the firmware and connect the phone to the computer via USB. Start MultiLoader.
Click "Search Port". The COM port should be available below. Select it.
Now select the files as following:
Boot Loader -> BOOT_LOADER.bin
USB Boot -> usbboot_z500_d05.bin
MODEM Code -> TMQZS.bin
SHP Rsrc1 -> Rsrc_Z500_*.cnt
SHP Rsrc2 -> Rsrc2_low*.cnt
SHP FileSys -> FactoryFs_Z500_*.bin
* depends on the firmware file.
Now click download, and accept the warning. The flash procedure should start and will take 10-15 minutes.
When done click OK and disconnect the cable. The phone will self reboot and prepare your file system then reboot itself once again and it is done.
Verify your firmware with *#1234#.
Good luck!