Ipad will not start up and only displays the Apple logo in centre of screen.My pc cant access ipad on itunes because there is a passcode on ipad. Help please!

Hi my ipad will not turn on and only displays the apple logo in centre of screen,i have tried switching it on and off but to no avail,the skider to turn it off does not appear on screen.I cannot connect it to itunes on my pc as it has a passcode lock and itunes tells me it cant access ipad until passcode is turned off,but of course i cant do this because ipad wont turn on! any help would be great ,thanks.