Sophos Anti Virus setup error while installing

Hi there,
I cannot install Sophos Antivirus on my PC with Windows XP cause of this error. I tried many installers from different sources and I still cannot install it. I don’t know what to do anymore so can anyone help me please to install Sophos ?
Thank you !

Error 3004. Sophos software cannot be installed. Some registry keys do not have the correct permissions. Contact your support personnel. If you do not click “OK”, this message box will close automatically after 60 seconds.
OK
