Pc running really slow

Since going from F-secure to Avast my pc is so slow from startup to just about everything I use it for. Had I not paid for subscription I would simply do away with it. Any help would be really appreciated.

  • Which Avast…? (Free/Pro/IS/Premier)
  • Which version…?
  • OS…? (32/64 Bit…? - which SP/Build…?)
  • Other security related software installed…?
  • Which AV(s) did you use before Avast…?