Software problem i turn off my cell & i changed the sim but after that i m trying to swithc on but it off totaly swithc off pls can u give me some advice for this problem

I turn off my cell & i changed the sim but after that i m trying to swithc on but it off totaly swithc off pls can u give me some advice for this problem

Try to put charger to phone and see whether it shows charging. if it shows charging than you can power on after a while. are if you have removed battery without switching off the phone to change sim card, than most probably your phone's software got crashed and you need to visit sony ericsson service point.