I am running Windows XP Professional and have just installed service pack 3 to try and resolve this problem. I can install other software but not Sage 50, when I try to do this I get the message error 1719 The windows installer service could not be accessed. So far I have uninstalled and reinstalled this service and followed the advice from microsoft and Sage regarding de-registering and re-registering the service. I have also downloaded and installed the latest windows installer. When I try to install Sage and have the services window open at the same time to monitor it I notice that the options to stop and restart the service which are normally written in blue on the left side of this window disappear and the boxes to start, stop, pause and resume become greyed out. Please can someone shed some light on this for me?