Accidentally deletion of C:\Windows\assembly folder! How to restore?

Question

I accidentally deleted C:\Windows\assembly folder from a Windows 8.1 setup while trying to remove a virus. Everything seems to be working fine except for a program I use called Gmail Notifier. When I am trying to run it, I get the following error:

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Gmail Notifier Pro
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System.InvalidOperationException: Unable to generate a temporary class (result=1).
error CS0006: Metadata file 'C:\Windows\assembly\GAC_MSIL\System.Windows.Forms\2.0.0.0__b77a5c561934e089\System.Windows.Forms.dll' could not be found
error CS0006: Metadata file 'C:\Windows\assembly\GAC_MSIL\System.Drawing\2.0.0.0__b03f5f7f11d50a3a\System.Drawing.dll' could not be found
error CS0006: Metadata file 'C:\Windows\assembly\GAC_MSIL\System.Xml\2.0.0.0__b77a5c561934e089\System.Xml.dll' could not be found

at System.Xml.Serialization.Compiler.Compile(Assembly parent, String ns, XmlSerializerCompilerParameters xmlParameters, Evidence evidence)
at System.Xml.Serialization.TempAssembly.GenerateAssembly(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, Evidence evidence, XmlSerializerCompilerParameters parameters, Assembly assembly, Hashtable assemblies)
at System.Xml.Serialization.TempAssembly..ctor(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, String location, Evidence evidence)
at System.Xml.Serialization.XmlSerializer.GenerateTempAssembly(XmlMapping xmlMapping, Type type, String defaultNamespace)
at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace)
at System.Xml.Serialization.XmlSerializer..ctor(Type type)
at GMNcommon.XmlHelper.DeserializeFromFile(Type type, String fullFilename)
at GmailNotifierPro.GNconfig.InitConfig()
at #=q$YdU$AduRda_0zhCK7yQwtksdhi3_Q0_59l8ERR4j7Y=.#=q3wCGQXNfC$D9ZtMMiULm6Q==(Boolean #=qShgfTCOCLMcWck9_Oe$AGw==)

I asked a friend to send me a copy of this folder, but as I see, he's also missing the following sub-folders:

C:\Windows\assembly\GAC_MSIL\System.Windows.Forms
C:\Windows\assembly\GAC_MSIL\System.Drawing
C:\Windows\assembly\GAC_MSIL\System.Xml

I also tried to install some .NET Framework packages with no success! Can someone tell me how can I find the following files and others missing.

Answer 1

Restoring the system to an earlier point using System Restore solved the problem and fixed the problem with Gmail Notifier.

Answer 2

Considering that Gmail notifier requires .Net 3.5 and it's included in Windows 8.1 you need a different approach. Microsoft supplies a .Net Repair Tool which should repair your assembly directory.

The GAC_MSIL directory contains JIT (Just In Time) compiled libraries. There's a possibility that you don't have the proper permissions set to create files. You can try running your program as an administrator to see if that will create the files you need should the repair tool fail you.