CyanogenMod HTC One X+ can't boot
Got it fixed :D with thanks to Izzy and Chahk
I did a lot of things so I'm not sure if I write down every step I took, but I hope it will help other users someday. This is what I did.

Restore manger

Install a restore manager (TWRP/ClockworkMod). I used TWRP which I installed by using WinDroid Universal HTC Toolkit: http://forum.xda-developers.com/showthread.php?t=2499926
(If you still have a working ROM, backup this now by booting in recovery mode)

Flash ROM

Check in cmd if your device is recognized with "adb devices". If not try "adb kill-server" followed by "adb usb". Check again with "adb devices". If recognized use "adb push cm-10.2.1-enrc2b.zip /sdcard/" (or your own ROM-name.zip)

Flash Kernel

Now you should flash your kernel, not like how I did it at the beginning. "fastboot flash boot boot.img" in cmd. (Check first if your device is visible with "fastboot devices".

Extra Tip

Install playstore with Gapps or manually by moving "GmsCore.apk + GoogleLoginService.apk" + "GoogleServicesFramework.apk" to /system/app/ and run a playstore.apk (in my case "com.android.vending-4.6.16.apk")