Default [FAILED TO FLASH] Help! I can't flash my X10 on Windows 8.1

Hello developers,

I have tried to re-flash my Sony Ericsson X10 and i couldn't. This is what i tried:

1) I have restarted PC and Disabled drivers signature enforcement (or how it is called)
2) Then i installed flashdrivers from Flashtool folder
3) Once i connect my phone in flashmode (pressing back button and connecting to pc) this is what Windows shows:




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I have tried to connect my phone on USB 3.0 and USB 2.0, once i connect it on USB 3.0 it shows SEMC device, but when i connect it on USB 2.0 it shows Unknown device or something like that.

Somebody knows how to fix that and if there's even a solvation for this thing? Or Windows 8.1 doesn't accept Sony device in flashmode anymore? Thanks for help! Waiting answers asap! By the way when i connect my phone when it's turned on Windows accepts it fine, i get these errors only when i connect my turned off phone to PC in flashmode to flash it.
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