Avast! for U3

In August of last year (2010), My desktop computer crashed and burned due to my wife accidently stepping on the switch to the surge protector, then turning it back on when she realized what she had done. Thus causing an electrical spike which fried the mother board. she had my SanDisk flash drive in when this occurred. I have since moved the surge protector up to the underside of the desk, saved every dime I could lay my hands on to replace the desktop with a laptop. I have recently replaced my SanDisk. My question is this: How do I go about replacing avast! for U3 on my flash drive. My licence is still current. It doesn’t expire until August 9, 2011.