I have problem.Its faced when I want to to unlock my bootloader. I use One V toolkit to unlock bootloader,but when It's say succes,there isn't option to unlock my bootloader 

 and I think its because the driver not work/missing.
so I try to search in google,and foundnd the solve from these post. first and second

 so,the steps are
1. Install sdk android (you can search in google)
2. Update the sdk android to have google

 3. Open device manager
2. Select the android device with yellow sign (if you have installed,just uninstall it and follow the instruction)
3. right click and select "Update Driver Software ..."
4. select browse my computer for driver software
5. select "Let me pick from a list of device drivers on my computer"
6. select HAVE DISK and browse for the "usb_driver" in the android sdk folder
7. select Android ADB Interface and press next
8. select yes, ...

 and test with your HTC tool kit.if you can use command reboot phone,ITS SUCCES 

and I Think It can use to other handheld,just use your improve and logic :D