Yes, it's totally possible to install Windows 7 (or Vista) on the MacBook Air without a DVD drive. All you'll need is a computer running Windows 7 (that has a DVD drive), a 4GB or larger USB thumbdrive, a Windows 7 installation DVD, and about an hour of free time.
Note: make sure you back up the contents of the thumbdrive as they will be completely erased during this process.
CREDIT TO CNET.COM Install Win 7 on MacBook Air from a USB drive
Note: make sure you back up the contents of the thumbdrive as they will be completely erased during this process.
CREDIT TO CNET.COM Install Win 7 on MacBook Air from a USB drive