How do I make a Windows 7 USB stick to install W7 on both OSX and a PC?

I've been following this guide and I've done everything up until the sudo command bit and the only thing I have actually changed is doing /rdisk2/ instead of /disk2/ as it allows for much faster writing.

Whenever I try and put it into the PC it doesn't recognize the drive as having a boot device on there

What have I been doing wrong?

Need help asap!