Upon your sound advice, I installed Mailwasher on my 2 PCs and it has only ever worked on 1. It thinks it's not connected to the internet.
Now I have just installed another program which requires it to connect too - and it also can't connect.
I'm assuming it's the same thing preventing both progs connecting.
Both PCs are wired to the same router/ADSL modem
No software firewall is running
Both PCs can browse websites/download etc OK
Any ideas why one PC is OK and the other isn't?
One thing - I disabled a bunch of 'unecessary' services a while back using services.msc as advised by blackviper.com