Can't get in recovery or normal boot HTC One M7
The first problem was that fastboot didn't connect to my PC.
This was solved by changing computer to one with a USB 2.0.

The problem I had with my recovery was solved by flashing the recovery partition again and cleaning the cache (forget that the first time).

fastboot flash recovery clockworkrec.img
fastboot erase cache


After this I was able to get into recovery mode.

I then had a problem where Android Revolution HD did not install and my HTC One M7 was stuck in a bootloop.

This was solved by installing TWRP instead of CWM recovery, and by changing S-ON to S-OFF.
I was then able to install Android Revolution HD.

Thanks for the comments and many thanks to "bored_stupid" on XDA-Developers who solved the installation problem for me.