Stopped working all of a sudden

I am using a Sony MPF920 Z/131 floppy drive and has been working perfectly fine until now. I recently have made some Boot disks and was all going well. The drive is still recognised in Device Manager and appears in My Computer but every time i try to access it, it always states that there is no disk in the drive or it is not ready. The power light is constantly on whether there's a disk in it or not. I even get the same problems with my optical drives. I am wondering if it's something to do with the power supply as recently had a new one fitted and was told that it ain't 100% compatible but closest one they could get hold of. Please help!!!!!!!!!!!!!!