I'm assuming that you are referring to these tutorials below.
1) Windows 7 USB/DVD Download Tool
2) USB Windows 7 Installation Key Drive - Create
Did you format the USB flash drive with a NTFS
file system first instead of the default FAT32?
- You can only create a 64-bit Windows 7 bootable USB flash drive if your current Windows 7 installation is also 64-bit.
- You can create a 32-bit Windows 7 bootable USB flash drive if your current Windows 7 installation is 32-bit or 64-bit.