Thank you for your reply. I will carry out the diagnostic tests you suggest. I should point out that we hire BT technical experts to look at any problems our applications have with windows. We contacted a BT support person who is an expert in problems caused by windows and malware and he carried out all the diagnostic tests not us and he could find no problems with windows or malware, and it was this expert who advised us to contact the Sqlite forum. It was my belief that the problem was not in any real sense a problem with SQLITE been incompatible with the latest version of windows but a problem with SQLITE caused by the installation of the update (which in both cases at first actually failed to install). For example, our "legacy" application uses a Pervasive (formerly Btrieve) database, and each time a windows update takes place it often but not in all cases overwrites one of the REGISTRY entries used by BTRIEVE and Btrieve then fails and becomes unusable till you fix the registry entry. Unfortunately, no amount of rolling back of an update or downloading new versions of windows fixes the error. and unless you know a little about Btrieve you have had it!! Unfortunately after an attempt to uninstall the update - the uninstall failed and Microsoft advised to get out of this problem the up-to-date version of windows be downloaded. And sadly there was no restore point and the BT expert advised it was pointless rolling back as after the maximum pause period the update would be installed again.