I have tried almost every thing to make a ClearOS bootable USB like LiLi(Linux live USB creator),one of my favorite UNetbootin, Grub and Grub for DOS but no success.Many times it boot but i was not able to install the ClearOS. Finally i got syslinux project and here is the way how can you install ClearOS from USB.
Download your ClearOS ISO and syslinux and follow the steps.
1. Format your pendrive with FAT32 partition with at least 1GB because ClearOS ISO have a minimum size of 600MB.
2. Mount or extract images and isolinux directory from your ISO image in your USB drive.
3. Rename “isolinux” folder to “syslinux“ and “isolinux.cfg” to “syslinux.cfg“ in your syslinux folder.
4. Extract your syslinux on your system. Navigate through command in win32 directory inside the syslinux.
5. Run command syslinux.exe -m -f -a -d /boot/syslinux e: (Replace e: with your USB drive letter)
6. Copy the ClearOS iso file to the root of the USB partition.
7. Plug-in your USB and start the system. In my case i am using f10 key to force boot through USB drive you can check your key according to your motherboard.
8. When ClearOS will ask where to find the installation software select Hard-Drive it will show both of your disk USB and Hard Drive. Select USB drive.
9. Else installation is common as the CD-ROM.