Having major issues with reformatting Acer Aspire One

computer is registering a windowsroot/system32/hal.dll file missing and needs to be reinstalled. I have been told to reinstall a copy of Windows XP. These computers have no optical drives yet they sent me a CD for reformatting the computer. Plugged in an external dvd rom, but it is not recognizing it nor is it allowing me to restore the computer.....
HELP! have a major presentation tomorrow and can't get information completed.