An expired version of the WBI Workbench exists in the registry. Can not install WBI Workbench 4.2.3 without first deleting the expired trial version from the registry. To delete the trial version from the registry, use the following procedure:
1) Using Desktop Tool bar click on Start>>Run >>,
2) Type Regedit and click Enter
Regedit Application will open.
3) Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
4) Find key "Classh0.2.1"
5)Right click to display popup menu.
6) Delete key "Classh0.2.1
Now you should be able to run Workbench.