I have downloaded the tMobile V4.0 handheld software, run the installer and sync'd but the upgrade to my handheld hasn't happened. I am new to Blackberry. The application loader says 'no system software found' what am I doing wrong?

Search your computer for a file called Vendor.xml move it to the trash then connect your BB it should prompt you for the upgrade. That being said when did you purchase you 7290? It most likely shipped with 4.0 to be certain from the BB home screen options --> about that will tell you your current vers. or OS.