Go to Start>Programs>ArcGIS>License Manager>LMTools
Open LMTools and choose the Service/License file tab.
Select 'Configuration using Services'. Click on the 'ESRI License Manager' service to select it.
Click on the Utilities tab.
Browse to your license installation location (ex. C:\Program Files\ESRI\License) and click on lmgrd.exe.
Click the Find Version button.