Sophos Install and Update failure

Hello,

I am having trouble installing sophos onto a windows XP machine with a error message 1621 and also using the same link which has been made on one of our servers I can install Sophos onto a windows 7 machine but sophos will not update, the icon on the bottom left says that sophos failed to update and when I go to update it manually by clicking on the icon it says sophos does not require any updates then goes onto attempt to install update service.

I assume that the install like isn't working but it was working fine when I was installing it to another computer half an our earlier. If anyone can help it would be most appreciated.

Thanks

Jonathan

(p.s sorry if ive posted this in the wrong section this is the first time ive used the forums)