When I start up my computer a message appears in the desktop area. The box opens as ‘RUNDLL’ with the following message: ‘Error in cwindowSYSTEMShell Ext arget.dll. Missing entry CDPlayNotify’. I’m not sure what I have done to cause this error, can you tell how to rectify and remove this error.

From the information you have provided, the problem is caused by Powertoys and, specifically, in the ‘TweakUI’ Powertoy where you enabled ‘Play audio CD’s automatically’. Powertoys are free non-supported utilities made by Microsoft to change little things in Windows which can make a big difference to the functioning of Windows (no mission critical settings though). To get rid of this error message at startup, I suggest that you firstly go into the ‘TweakUI’ control panel (in ‘Control Panel’), click the ‘Paranoia’ tab, and deselect the option to ‘Play audio CD’s automatically’. Finally, I suggest that you uninstall all of the Powertoys. I assume that the reason you used the ‘TweakUI’ control panel to automatically play CD’s was because your CD’s were not playing automatically by themselves. If you are having this problem, I refer you to the previous question in this column where I detail how to set up audio CD’s to play automatically.