Stuck on pink circle but have no idea wat im doing lol

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http://forum.xda-developers.com – Hi all, just bought a hd2 the other day for a tenner since previous owner didnt know what was wrong with the device, which brings me to my problem. When i try to start up the device it boots to a pink circle that just hangs, im not sure what it was running before (wm, droid, etc...) so i was hoping one or some of you may be able to spread some light? :) P.s. Im not a total noob with android but i dont know if its a droid or not lol. Thanks in advance :) sent from my baby xperia tipo via the xda android app (HowTos)