Avast can not work

today , when i start the system , avast can not work, an error message comes out which shows below, and i try to reinstall the program, the program persists.

http://www.2dai.com/forum/attachments/month_0604/Image00005_Xene7Ut3owuK.jpg

http://www.2dai.com/forum/attachments/month_0604/Image00006_YSa6vEz7fj2g.jpg

“Error :System can’t open designated devices or files”