is there a way to reset the Mac Book air?

Follow this link and you'll be good to go: http://support.apple.com/kb/ht5189

What to do before selling or giving away your Mac

If your model came originally with Snow Leopard or earlier:

Clean Install of Snow Leopard

Be sure to make a backup first because the following procedure will erase

the drive and everything on it.

1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.

2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled, if supported), then click on the Apply button.

3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.

4. When the installation has completed your computer will Restart into the Setup

Assistant. Be sure you configure your initial admin account with the exact same

username and password that you used on your old drive. After you finish Setup

Assistant will complete the installation after which you will be running a fresh

install of OS X. You can now begin the update process by opening Software

Update and installing all recommended updates to bring your installation current.

Download and install Mac OS X 10.6.8 Update Combo v1.1.