Your computer needs to meet the minimum system requirements to display the lesson links. This includes the need for a web browser (Internet Explorer 5.5 SP1 or higher). If you are using anything lower than IE 5.5 SP1, you could get a white screen and not see the lesson links. This is needed for the windows to operate properly.
You can download Internet Explorer 6.0 SP1 from the link below.
http://www.microsoft.com/downloads/details.aspx?FamilyID=1e1550cb-5e5d-48f5-b02b-20b602228de6&displaylang=en
If this fails to resolve the issue, you should also check the security settings for Internet Explorer. Try changing the settings to Lowest. Make a note of what those settings were before you change them. This way, you a reset them back to those settings after using PC Tutor.