Sounds familiar... My son upgraded his X50 to WM5, a few days later it refused to boot. Dell tech support diagnosed it as hardware failure and replaced it under warranty. He upgraded the refurbished replacement - which worked until two weeks after warranty expired. Same failure. He replaced it with an iPaq and vowed never to own anything else with Dell on the nameplate. Rather than leave the corpse on his desktop (and because I didn't own a PDA), I paid the "repair" bill and became an Axim owner. As you can imagine, I'm a little hesitant about upgrading to WM5.
His "hardware failure" sounds a lot like the 80% boot failure mentioned here:
Need Help: can't reboot
