Thank you both for quick replies, Yes preinstalled Dell security programmes removed long ago and opted for AVAST as sole Antivirus programme (earlier versions of Avast did run successfully so no conflicting programme were/are present). CCleaner has been used a number or times since their removal as well to remove any traces along with manufacturer’s cleanup utilities.

Only Anti virus presently installed is Avast Free (now ver 6.0.1091) though ZoneAlarm is and has been installed/updated for a number of years and is the currently active firewall. Windows Firewall is turned off.

Re Cleanup utility: a couple of weeks ago when problem first occurred with Avast 5 did an add remove programs uninstall of ver 5 (no longer have that full version number but it was whatever was the then current update) then also ran aswClear for both versions 4&5 and yesterday after Avast Free 6 failed again did an windows uninstall of that followed by another aswClean in safe mode for version 6 prior to the the current failed install of Avas version 6.

Yes, around Mar 21 there were a number of Windows Vista updates installed and we have tried unsuccessfully to do a windows restore point to just prior to that time but the restore failed so short of running the Dell windows full restore CD to “Out of box” configuration can’t do a Windows repair without reinstalling all programmes and personal data which is of course the last resort we are trying to avoid if possible.