Thank you everyone.

Ali, they say great minds think alike, and I was just looking at that same page that you gave me the link to.

I haven't found an answer yet, but there was a similar question where some-one's computer froze each time he accessed Skype. His problem was due to an Internet Security issue.

Frank, you mentioned that the firewall might be blocking Skype and I may need to add it to the exceptions list. Would that be a Windows firewall thing, or to do with my McAfee virus scanner. And....how do I do that please?

The Q's & A's also mentioned that CPU usage could be a problem. I checked all my non system CPU's and there didn't seem to be anything untoward there.