and the associated link for XP (which should be close enough to any windows OS that you already have).
Strike that. Try this for making your USB Flash Drive into a bootable Windows 7 drive.http://www.intowindows.com/how-to-install-windows-7vista-from-usb-drive-detailed-100-working-guide/
As for whether or not you can boot from a USB drive, shutdown your system and then restart it. You should see a message early during the boot process that states something along the lines of, "Press F2 to enter Setup". What key it actually is, I don't know, but it should be either F2, Del, Ins, something. This will bring you into your BIOS screen. Somewhere in your BIOS screen you should see an option of Boot Order. If USB is listed there, you can boot from it. Since the system does not natively have an optical disk, I would imaging that it should be there. When you're ready to install the Windows 7 from the USB flash drive, go back into BIOS and change the boot order so USB is first.