On start up I get an AVG screen warning me of a Trojan horse dialer virus.
I've tried quarantining & healing which solves the immediate problem but I'm
still getting the problem after start up. If I don't immediately deal with
it the system crashes & I have to reboot.
I would appreciate any help in getting rid of it permanently.

Geoff Newbould.

>On start up I get an AVG screen warning me of a Trojan horse dialer virus.

No such thing as a "Trojan horse dialer virus". What it likely is would be a
porn dialer, which is adware. Try a spyware removal program. There are a couple
of free ones such as Spybot and some that have a yearly fee such as Spy
Sweeper.