I installed a avg on my friends computer and after a week or two she said that all the info on her computer is?

gone. i have not looked at it let but if it is is there a program or anyway to get i back. i know if you have a backup disc but i dont think she does. any other way. also i installed avg on my three computers and nothing happen to my and it been 3 years same programs she has. and i installed avg twice because license expire. so i know it cant be avg. also if you can tell me what could have happen it would be great thanks