S1 boot Fastboot problem

So, my dad just got me the Xperia Z2, and I've been searching for a solution to this problem over the Internet for hours, no luck. When I connect my Xperia Z2 to the Pc in Fastboot mode, it gives me an exclamation mark in the device manager on S1boot Fastboot driver, so Fastboot doesn't recognize my phone. What should I do?

Edit: My bootloader is unlockable, I've checked through that dialer command. Just saying if anyone is going to ask.