Avast pro

I have bought and paid for a one year Avast Pro “TWICE”…once in May and had no success with setup etc. Downloaded and attempted to setup again and FAIL…what is happening? I have windows XP and when I download the program it seems to be fine and in my downloads folder…then when I click to execute it just sits and spins…sits and spins…I am gettng dizzy

have you removed previous used AV before installing avast?
have you used the vendors removal tool to clear any leftover files that may conflict?

tools here. http://singularlabs.com/uninstallers/security-software/