It won't recognise adb if you can't get it into either android or recovery.
Can you boot into fastboot (boot while pressing "volume down" to get into the bootloader, then select fastboot) and flash a new recovery? You need the fastboot program installed on a computer to do this, but I'm hoping you have an unlocked bootloader and installed the recovery this way originally, in which case you just need to repeat that process. If you can do this, then boot into recovery and restore your backup (you did take a backup first?) or flash a different ROM (make sure it's a good download and compatible with your phone).
If you used some other tool to install the recovery and the bootloader is not unlocked then you probably can't do this. In that case your best bet may be to find a suitable ROM Update Utility (RUU) for your phone. Put the phone in fastboot mode, connect to a PC via USB and run the RUU (which is a Windows .exe) on the PC. That will reflash the phone with a fresh set of HTC software. However, you have to get the right one for your phone's branding, which means I can't suggest one here without more information.
You may find some more useful information here:
Explorer - All Things Root - Android Forums
My normal source for RUUs is shipped-ROMs.com, but they don't have many for the explorer:
Shipped ROMs
Good luck! For something like this we probably could help more if you registered with the main forum, as it's easier to actually discuss there.
