Installing latest possible firmware and Android on HTC Desire HD I have installed CyanogenMod on my HTC Desire HD a while back. Some things don't work, so I'd like to do these things:


Install latest possible firmware
Install latest possible standard (non-HTC) Android version
If compatible with above, install rooted version (not really necessary)


What steps do I need to take to do the above? Where and how can I find all necessary files to do this?
There is no "standard non-HTC" version of Android, your device needs custom drivers and therefore a customized version of Android.  If you install a custom ROM it will most certainly be pre-rooted.

You should check XDA's Desire HD development subforum for custom ROMs.  Read a few threads and decide on one that sounds good, then follow the instructions to flash it.  If there are no instructions then just put the ROM .zip on your SD card, reboot into ClockworkMOD recovery, and follow the menus to flash it.