Quick notes and probably last reply from me, I'll try to cover every aspect of your problem.
-RUU is a Stock ROM which should be in .exe format to run through pc while device is connected.
-To play around with device,doesn't necessary to be a developer.
-I'm also not a dev but if you spend more time here,you'll learn a lot.
So cut the crap and head over your issue.
now i don't know which carrier your device is locked Or from where you bought the device. But RUU should be from that carrier origin or at least country origin.
Check here: http://www.shipped-roms.com/index.ph...roid&model=Ace
These are stock rom for our device(Ace-code name of Desire HD/Inspire 4g)
Choose one with ending of .exe and according to your carrier or country from where you bought it.
As earlier you've mentioned that you may able to get into Fastboot,then put your device in fastboot mode and it should be in Hboot USB ,now to go into such way you need to connect your device through USB and wait a second or so then press power button and it will show you in RED color.
After that run RUU file through pc by double clicking on file. It will prompt you that it will upgrade your device hboot version,go ahead and click next. and let the process complete. But before all make sure your device has more than 30% of battery. If you encountered any problem,then head over to htc.com and ask for help regarding it. I'm just saying because your device is in Stock mode,nothing has been changed according their standard. Or you may look at here in forum regarding error that you get while running RUU.
If you successfully go through all steps,then your device probably back to life again,unless there isn't any hardware issue. Once you deal with this you may now able to unlock bootloader and root your device. But that's only when you actually done with above mentioned steps.
If some point you don't understand what i'm saying,then from my side i'm SORRY. But you've to spent more time with your device in order to learn it properly.
With considerate help, I rooted another phone so am confident to push the margins as you implore me to do. I'll get on with it!