# .NET and More > Silverlight >  Unable to Start Debugging. The Silverlight managed debugging package isn't installed

## ERUM

I  have silverlight 3 installed on my computer and i m getting this error(see title) when  run application 

secondly few days ago a site need to run on advanced version in silverlight i think 4 .so installed that ,afetr that i  m getting an error ,what shoud I do .





any help..

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## MattP

Your Silverlight Developer Runtime wasn't updated when you upgraded Silverlight to version 4.  You'll need to install a current version.

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## ERUM

i m getting same error i have following stuff installled on my machine 

see attached image

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