Avast does not run on startup and whwn i start avastui from Program files it does’nt start i can not even uninstall avast. I cannot even download another antivirus.once avast started and i choose boot time scan because of its been long i cancelled it at 4%. But there were 80 infected files
please give a solution
how many virus programs have you installed. 
for help in removing virus follow this guide and attach the logs. http://forum.avast.com/index.php?topic=53253.0
we need Malwarebytes / OTL / aswMBR logs
when done a malware expert will help you clean the computer
Only avast and now i have turned firewall on after problem with avast