You can create a scheduled task that will run when your computer is unlocked:

1. Start > Administrative Tools > Task Scheduler
2. left pane: select Task Scheduler Library
3. right pane: click Create Task… (NOTE: this is the only way to get the correct trigger)
4. in the Create Task dialog:

General tab – provide a name for your task

Triggers tab -- click New... and select On workstation unlock
Action tab -- click New... and click Browse... to locate your script
Conditions tab -- uncheck Start the task only if the computer is on AC power