if you have installed the ROM image, you won't see the O2 splash screen any more. it will change to generic HTC splash screen
if you still getting O2 splash screen and getting stuck at the startup that means, you have not installed the ROM image.
post your problem with more details
ok, lets try a different trick
do a hard reset instead of reinstalling the OS hpe this might fix ya device
Hard ResetHold down the Power button (Top Right corner) and at the same time put your Stylus pen in the hole where it says “Reset” (Lower Left corner).
Hard Reset will delete all data you have put on the device, Programs, Settings, Mail, SMS, MMS, etc., so be careful and make a backup before doing this.
After a hard reset, you will have a complete clean new install of Windows Mobile on your device.
OR
1.goto boot loader
Boot Loader Mode
You can enter or exit bootloader mode by pressing the camera button, power button and then the reset button and hold for a few seconds.
or try this press and hold power+record+camera the same time and then reset
2.connect your phn to pc via usb data cable (do active sync on the pc)
3.run the MAupdreadeNoID.exe on your pc from the package i gave you
this will reinstall/upgrade to WM6.1 (originaly phn comes with WM5)