Hi @Moochi
If your are a Linux user and to be able to run PC Companion, you can use a virtual machine running Windows OS installed in a VirtualBox environment.
https://www.virtualbox.org/wiki/Downloads
Once you have installed PC Companion in the virtual machine, I suggest you to first run a backup of the device information like this:
http://talk.sonymobile.com/t5/FAQ/Backup-amp-Transfer/m-p/407253#U407253
Try performing a system repair using PC Companion:
http://support.sonymobile.com/gb/tools/pc-companion/
This will factory reset your phone and erase all data. You might need tocharge your device for about 1-2 hours before so the device has at least 80% battery. Make sure the device is not connected to computer or laptop and turned off (sometimes you have to press power button and volume up until the device vibrates 3 times or on some devices you have to press the small button near the SIM tray or on the back of the device). Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the on screen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process. If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP.
In PC Companion you press start on Support Zone -> Start on Update the phone/tablet software -> Repair phone/tablet (the blue clickable link in the message) -> Follow these steps without having your device connected to the PC.
Follow the instruction that appears in the program and do not connect your device until this guide tells you how to connect it.
If it's not possible to perform this software repair, you could check the following FAQ topic regarding USB connection problems:
/t5/FAQ/USB-connection-problems/m-p/348074
I'm at disposal for any question.
Best Regards,
