Did you reboot after uninstalling your prior version of Windowblinds?
Did you turn off your AV software before downloading and installing the new version?
If the above doesn't work, Please contact support for assistance.
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Stardock Sales and Support are open Monday - Friday (9am-4pm EST).
Every effort is made to respond to queries as quickly as possible, though emails sent after-hours and on weekends will generally not be seen until the following work day.