Avast wont start-up

I was installing a program and my computer crashed but when i restarted avast wouldn’t start up.
I went into the control panel>services>start an got an error>ERROR 1053: THE SERVICE DID NOT RESPOND TO THE START OR CONTROL REQUEST IN A TIMELY FASHION.
Ive un-installed/re-installed,no good and for some reason.i cant restore to an early time,so i think i may be infected,any ideas cause it looks like im gonna have re-install the whole o/s.