Updating to windows mobile 5
The way to do this is to run a “Soft SPL”, which will temporarily allow you to flash a new bootloader onto your phone (called a Hard SPL). Make sure you have removed your SIM card, SD cards, etc.
Everything is backed up in the flash memory, so unlike prior devices, WM5 devices lose no data if power is lost.
This version featured increased battery life due to Persistent storage capability.
Previously up to 50% (enough for 72 hours of storage) of battery power was reserved just to maintain data in volatile RAM.
This is where you have fun trying to find a custom ROM that has been tweaked for your model phone.
I just went with the most recently updated version for my phone Windows mobile 6.5 ROM for HTC Touch dual