go to startup (type msconfig in "run")
check the startup tab for any entries of
"C:\windows\system32\semtiantivirus"
if present uncheck it, or, I think by now u've Ccleaner installed in ur PC

,
In Cleaner, go to Tools>StartUp
Search for the same entry, if found delete it.
Reason: I think the file was included in ur startup, as soon as windows used to boot, it used to start. Now that u've deleted the file manually, as windows start it can't find the file throws d error.
Check this and reply.