Cannot create USB bootable drive for Windows 7 Home Premium 64bit

Daemon Tools is not compatible with Win7 and can cause problems. You can mount a .vhd in Disk Mgmt: Virtual Hard Disk - Create and Attach VHD

I gave you the steps that include everything you need including a new official installer ISO and the tools MS provides to burn to DVD or stick: Clean Reinstall - Factory OEM Windows 7.

If you stick with the tools and methods in the tutorial then you will get and keep a perfect install for as long as you do, since it compiles what has worked best in tens of thousands of installs we've helped with here.

I do follow the instructions.

But after I create a boot USB using "Windows 7 USB-DVD Download Tool" I try and check that all is well, open the content of the USB and the entire size is about 90 MB.

This I cannot understand.

Which program did you use to write the Win7 ISO file to the flash stick? The MS tool for this is in Step 2 of Clean Reinstall - Factory OEM Windows 7 - Windows 7 Help Forums.

You said you are following the steps. Did you use that tool from Step 2 to write the ISO from Step 1 to the stick. If so it should be bootable. Start over now and do that.