I'll second the USB flash drive idea. I just recently reinstalled Windows 7 on my UL30A (no DVD drive) using this method.
A few things to note:
- You'll need an existing computer with a DVD drive that can read the Windows disk
- You'll need to use a specific program on the Windows disk to make the drive bootable (see the guides wiretap posted)
- You'll need to copy the entire contents of the Windows disk over to the flash drive, so make sure yours is big enough
- Make sure the target computer supports booting from USB (removable device); most do these days, but you might want to Google it quickly first
- Installing from USB is generally a bit faster than installing from the DVD itself