Thank you to everyone who answered my question.

This morning, I stopped by the store where I bought my pc, to ask their
technical guys about the virus problem.  I needn't have worried.
Fortunately, when I got my computer, I got a quality machine that doesn't have
this defect.  It turns out that only computers that have a serious fault in the
software are capable of being infected by one of these viruses, what the
technical boys referred to as 'junker' pc's. Apparently, the market is awash
with them, so be warned if you are thinking of buying.

Once again, it seems that you get what you pay for.

Andy.