I'm currently trying to get into fastboot mode on my Xperia U but to no avail. The green LED comes on for 4 seconds before switching the phone on completely. Checking device manager it says that the device enumeration has failed and is unrecognised despite me installing the drivers at least 7 times. I have so far installed the drivers in flashtool in the driver signatureless option and I have double checked everything. Does anyone have any ideas?