tried that but I could only manage to relock the bootloader with it
OK so here we go:
1. enter the bootloader mode
2. enter "fastboot" menu from bootloader
3. Connect phone to computer using the usb 2.0 port on your computer/laptop
4. Google "mini-sdk" and download the files
5. Move "mini-sdk" folder to desktop
5b. Download twrp or cwm recovery for your phone by googling "twrp HTC ___" (Your phone model in the ____)
5c. Rename the recovery file to "twrp".
5d. This recovery file will be .img in the ending in the file type (skip if you don't get this step)
5e. Move this recovery file (called twrp.img) to the mini-sdk folder on desktop
6. Extract the mini-sdk folder if it's already not
7. On the "mini-sdk" folder there should be 4 files. Make sure there are 4 files or more.
8. In the "mini-sdk" folder hold down "shift" key and while holding "shift" do a right click
9. After "shift + right click" in the "mini-sdk" folder click "open command prompt here"
10. In the black screen that opened called "cmd" type in this without the " " ----> "fastboot flash recovery twrp.img"
11. The computer should then flash that recovery onto your htc device.
12. Now, download a rom for your device using google (I prefer cyanogen mod as it is easy to install)
13. Download the .zip file for the rom and place it into the "mini-sdk" folder.
13b. When you are on the cyanogen official website for their rom (highly suggest using this) they will be 2 files to download. One called the rom (cm 11,12) and one next to it the recovery that goes with it. Download both
13c. Also place the cyanogen mod recovery file which was next to the rom on their website in the mini-sdk folder.
13d. Rename the cyanogen rom to "cm" and the cyanogen recovery to "cwm"
14. Now, boot your phone into the twrp recovery you installed and your htc should connect as an mtp with the computer.
15. Using the computer, transfer the mini-sdk folder to the internal storage of your phone (create a folder in the internal storage called cyanogen)
16. Now get to your phones bootloader again and go to the fastboot menu
17. In the black window (cmd) that's open on your computer, type "fastboot flash recovery cwm.img"
18. Once this recovery is flashed go to your phones bootloader and then click recovery. The recovery should now be changed, it should be different looking than the twrp one.
19. Now go to wipe cache and wipe the cache
20. Go to install, install from sd card, and locate the rom called "cm" in the "cyanogen" folder you moved to your htc phone from the computer. Choose the zip file (cm.zip) and install it.
21. Once it is installed reboot your device.
22. It may take couple of minutes, be patient.
23. Your phone should now boot into the new OS.
Congrats!