Thankfully, that appeared to work. After creating the new file I re-installed AVG and removed the email protection (bit apprehensive about that) and everything is working again.
Many thanks for your...

That makes sense, Ken. Some time ago, a colleague did some work on my PC for me and it may well be that he created the .pst file on one of his own sticks at that time as "temporary" safety.
If your...

Since updating to Win 10 in October 2016, I have relied on Windows Defender together with MalwareBytes and SuperAntiSpyware. This morning, I installed AVG Free having checked extensively on line re...