C-RoM is releasing its awesome firmware now based on Android 4.4.4 KitKat AOSP for various Android devices. You can now install Android 4.4.4 on HTC One M7 too using C-RoM custom firmware. Including some amazing features, clean look and a good level of customization, C-RoM offers a fast experience that is both smooth and stable. 
C-ROM Android 4.4.4 details:
- Peek
- App Side Bar
- On The Go Mode
- Pie
- Floating Windows
- Active Display
- Animation Control
- and much more!
Prerequisites to install Android 4.4.4 on HTC One M7 with C-ROM:
- Backup any important data as a complete wipe will be required during the flashing process.
- Enable USB debugging option on your device from developer options.
- Ensure that ADB and Fastboot is correctly configured on your PC
- Your HTC One M7 should be having a recovery tool like ClockworkMod or TWRP.
- Juice up your device to at least 60% of power.
How to install Android 4.4.4 on HTC One M7:
Required files: download the C-ROM Android 4.4.4 KitKat from here and extract the boot.img file.
- Connect your device with computer using a USB cable and copy the firmware file on your device' SD card root.
- Copy the boot.img file to android-sdk-windows\platform-tools directory and then disconnect your HTC One M7 when the copy is done.
- Switch off your phone now and reboot into Bootloader / Fastboot mode.
- Turn your HTC One M7 back on while pressing and holding the Volume Down + Power buttons.
- Once in the Fastboot mode, navigate to the android-sdk-windows\platform-tools directory on your PC and open Command Prompt with Shift + Right-click > Open Command Prompt. Type the following command:
- fastboot flash boot boot.img and press Enter
- fastboot reboot; press Enter.
- Follow the onscreen instructions and then select Bootloader > Recovery.
- Once in CWM, perform wiping tasks: select wipe data/factory reset followed by wipe cache partition and then finally wipe dalvik cache (from advanced).
- Return to the main screen and press Install zip from SD card > Choose zip from SD card and locate the downloaded Android 4.4.4 firmware file.
- Confirm the installation and Reboot your HTC One M7 when finished.
Awesome! You just have flashed Android 4.4.4 KitKat with C-ROM on your HTC One. First boot takes a while so please be patient.
