Default [Q] HTC Desire HD not recognised - can't install custom ROM's problem with fastboot

So basically i followed this guide - wiki.cyanogenmod.org/w/Install_CM_for_ace

Let's start from the first part wiki.cyanogenmod.org/w/Install_CM_for_ace

I plug in phone, i can see it in my PC as D drive but nothing more, after command "fastboot devices" i get 0 info - just like no devices were connected, but after i write "adb reboot-bootloader" my phone goes into this white screen. After this message about unrecognised device connected to USB appears. From now i can't use command "astboot flash recovery your_recovery_image.img"

I also has question, what does command "fastboot oem get_identifier_token" stands for? After writing this command i get info "waiting for device....".

I've also has question - why I unlock phone? What does it stands for? Does unlock means the same as rooting phone?

My System is Windows 8.1 64 bit.

Maybe i should install some HTC drivers or something like this? I installed HTC Sync, then uninstalled it, so just pure drivers should be left on PC but it still do not help me :/

USB debugging is on.