So on your computer you have a shiny new copy of Windows 7 in ISO format. Now the next question is how to get it unto your Asus EEE PC. A USB Bootdisk of course (you could burn a dvdr, but why waste it). So here is the procedure I had to follow to get mine to work.

Things you'll need:
USB drive > 4GB
Windows 7 in iso format
UNetbootin (link)
a running version of Vista

1) First step is to use UNetbootin to get the contents of the ISO onto the usb drive.

2) Wait while things are copied to the disk.

3) Remove a couple of files from the USB disk after UNetbootin is done:

a) vesamenu.c32

b) syslinux.cfg

c) ubnfile.txt

d) ubnpath.txt

e)ldlinux.sys

f)bootmgr

4) Use whatever method your comfortable with to get the drive letter for the device (In this we're going to say that my thumb drive is E:).

5) Now bring up your command line (usually Start Button → Run & type cmd then enter). And put the following instructions in it:
bootsect /n60 e:

6) Now close out the command window, safely disconnect the thumb drive, and your ready to boot up windows 7 on that awesome EEE Pc of yours... or someone else's.