There are several ROM upgrades available for the Hermes, you can find them in the Shipped Complete Updates wiki page, be sure to read the notes on this page before you start the ROM upgrade.
Please DO NOT ask which is the best ROM for you, the Hermes upgrading forum is flooded with this question and we can't really give you an answer: a ROM upgrade is only as good as the comments it has received from the users on the forums, see the top right column of the Shipped Complete Updates table for each ROM's forum link.
Before Running the ROM Upgrade Utility
Before you run the ROM Upgrade Utility (RUU), make sure you check that the ROM is for the Hermes, if it was for any other device it will brick your phone and do the following first:
BY FAR THE SAFEST AND BEST WAY TO UPGRADE IS TOUpdate Rom using MicroSD card. If you do not have a MicroSD card (2GB or less) then use the following method but be warned: many, many people have bricked their phones using it. It is especially dangerous if your ROM upgrade has a Radio in, as a failure in Radio upgrade is the most difficult to recover from. Make sure you install HardSPL first as this MAY help to recover if bricked.
USB sync cable is connected to the computer.
You have the Microsoft .Net™ framework installed on the Computer (Vista users see below)
The standby and hibernation modes are disabled on the computer.
All running applications on the computer have been closed.
USB sync cable is connected to the phone to establish an ActiveSync connection with the computer.
Do not interact with your device unless instructed to do so.
Make sure your PC is stable and there are no breaks in your USB connection (i.e bad USB port) as this will result in a 'bricked' (dead) device.
Please note, Windows VISTA users need to use a slightly different procedure to get their machine ready to use the ROM updates - which is documented excellently (with illustrations!) by Mr. Vanx here.
General Procedure on Installing the ROM Update
Back up your personal data from the phone to your computer using ActiveSync if you want to ensure you don’t lose any of your data.
On your computer, run the ROM Update Utility (RUU) to install the ROM update to your phone. (The next section provides a detailed procedure on how to install the ROM Update).
Restore your personal data back to your phone using ActiveSync. (Optional)
On the Welcome Screen, click Next to begin the ROM update installation.
On the next screen, follow the listed instructions in the dialog box first. When you are done, click Next to proceed.
Note: You should read and follow all the instructions listed before clicking Next.
The following message will then be displayed, indicating that the utility is verifying and acquiring information about the device as preparation for the update process. Wait for this verification process to finish.
Current information about the device, such as the model ID, image version and language will then be displayed. Click Update to proceed.
Below the device information, information about the new ROM update will then be displayed. If you are certain that you want to install the phone with the new ROM update, click Next to proceed.
A confirmation message then appears and shows the length of time it will take to copy the necessary files (including radio image) to the device. Click Next to begin the update.
A progress bar will run through the screen during the update process.
Note: In the middle of the update process, the progress bar may stop running. This is normal as the RUU is adjusting itself to complete the update process automatically.
When you see the screen below, it means update is complete. Click Finish to exit the utility.
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