Thanks for your replies Chris and Armeen,

After shutting down my computer last night and restarting it this morning, the task bar icon is showing correctly now. I think it may have been some caching issue with my computer. When I originally built the Powerclient project it failed because my resource files all used absolute paths so I've had to change the application and the resource files to use relative paths.  I didn't change all the application paths to relative paths before I first successfully built the Powerclient application, so I think the very first time I ran the application it wouldn't have had the application icon embedded.  Even after updating all the paths to relative paths and the icons working correctly it still used the incorrect taskbar icon that it probably would have used initially.

Glad to say a restart fixed it.

I've got a few other questions about the Powerclient and project organisation, but I'll read up first and see if I can find the answers, otherwise I'll be back with more questions.