As a number have been flashing their devices with various roms not from their own carrier or country or cooked roms and bricking their device - I put up this sticky. Your device must be cid unlocked first before you do this. This applies to the coming wm6 roms to - if the rom is not specific to your device - i.e. if you try to flash the upcoming htc 3300 wm6 rom on O2 orbit - you must cid unlock first - with imei check or you will end up with a BRICK!
This does not apply if you are only updating the os http://forum.xda-developers.com/showthread.php?t=299154 or radio.
cid = country id i.e. locked to that country/language/vendor
cid unlock for the artemis is here with USPL http://forum.xda-developers.com/showthread.php?t=311403 (thanks pof)
or here http://www.imei-check.com/c3unlock.php (costs though)
If you have flashed your device and not cid unlocked it, your device maybe salvagable if you can get it into bootloader mode.
Hold down the voice speed dial button and soft reset - you should then enter bootloader mode 'multicolored' screen'
If you do, attach device to pc via usb cable (a small usb will appear bottom left of screen) and flash factory rom. (run rom executable or RUU updater from pc) You do not need to be activesynced to do this.
HTC P3300 WWE factory rom downloadable here http://rapidshare.com/files/19322112...0_WWE_SHIP.rar
Dopod P800 WWE factory rom downloadable here http://rapidshare.com/files/21058219...0_WWE_SHIP.rar
O2 Orbit WWE Wm5 factory rom downloadable here http://rapidshare.com/files/41574866/Arteimg.nbh
Before you flash again with a non-factory rom, your device MUST be cid unlocked.
If you cannot enter bootloader mode your bootloader has been damaged and your device will need to be sent away for repair.