from your posting it doesn't look your bios supports booting from usb dvd drives.
all's not lost though.
if you have a usb stick big enough you could make that bootable.
this would require a couple of tasks,
1, you'll have to turn your Windows 7 dvd into an ISO. basically a file copy of the complete dvd.
2, you need to make your usb bootable and copy the iso onto it.
1. can be achieved by using any free iso ripping software. I use Magicdisc from here myself. Mount ISO Files - Freeware MagicDisc Download
once this is installed it hides away in the systray, the icon is a hand cupping a cd.
if you right click this icon then select make iso from dvd/cd
you need to give a file name, nothing flash needed, sometimes I copy the cd label but it's not important.
you also need to change the output type to ISO, this however is VERY IMPORTANT. save this file to the root of c: or somewhere you have space, not the usb key though. lol.
2. download this app Download UNetbootin, Universal Netboot Installer from SourceForge.net
once this is installed it's pretty intuitive how to use it.
Oh I forgot to add this is VERY important also any data you have on the usb stick will be deleted so make sure you copy stuff off first. preferably not onto the computer you want to blast away either...
let use know how you get on.