Phone Stuck On Preparing Phone Memory

[iamtalha]

Ok so the main problem with my phone is that i was making a bootable flash drive and accidently transfered the files into my phone memory and after that whener i turn it on my phone boots to android and gets stuck on preparing phone memory i have even tried custom roms none of them work................ i have an lg optimus 3d su760...... can anyone tell me a way to format my internal sd card without turning my phone on cz it gets stuck before i can turn usb storage on??? anyone know a solution?

 

[iamtalha]

i would really request the senior members to help me out