For starters to clarify
WindowBlinds appears to be activated on this PC
This indicates purchased version yet in thread title you talk about trial, if you have purchased version, why would you install trial.
If trial is installed, uninstall it, reboot, run something like CCleaner, reboot, reinstall thru Stardock Central the purchased version to get latest build ( not sure what that is for vista.
Also if you have purchased version you may want to go to your settings page here and cross reference email, you show as visitor but if purchased WB should be current customer or past customer depending on when purchased. Both of these give you more download cap than visitor, current customers get unlimited for the apps the have bought.
is there a specific (version) of window blinds I could try
WB 5.50 is Vista 32bit compatible, 5.51 is first with Vista 64 bit support