Add note about error MSB4006

Error MSB4006 might occur after converting a vc80 project to 90 and
above.

readme.txt

@@ -34,8 +34,18 @@ See Help/compilersetup.html
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 Windows users (Visual Studio 2008 and 2010)
 -----------------------------------------
-Load RakNet_VS2008.sln and convert if necessary.
-If it doesn't work, see Help/compilersetup.html
+Load RakNet_VS2008.sln and convert if necessary.  
+
+After the project conversion, if you encounter error MSB4006,
+follow the steps below to fix it:
+
+1. Open project properties
+2. Click on "Common Properties"
+3. Click on "Framework and References"
+4. Look under "Build Properties"
+5. Change the "Copy Local" flag from "True" to "False"
+
+For other compiler issues, please see Help/compilersetup.html
 
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 Windows users (Visual Studio 2005)