You may need to try more than one method to successfully write the ISO to flash stick:
Windows 7 USB/DVD Download Tool
USB Windows 7 Installation Key Drive - Create
How to: install Windows (any version from XP to Win7) from a USB/flash drive | Featured | dotTech
The one that always works for me is loading ISO into UltraISO trial version, then on Bootable tab: Write disk image file, use format button first.
To boot stick use one-time BIOS boot menu, sometimes listed under HD's.