Try the following steps
1) Close QTP and any other application.
2) Open a CMD (command prompt)
3) Navigate the following path on your local file system: <<QuickTest installation folder>>\GlobalAssemblyCache\Net4
4) Execute the following commands:
..\..\bin\GACRegUtil4x86.exe -i Mercury.QTP.Agent.dll
..\..\bin\GACRegUtil4x86.exe -i Mercury.QTP.WpfAgent.dll
5) Check if this works, If no then try steps from 6 to 8.
6) 1. Copy from "C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Net4\Mercury.QTP.Agent.dll" to this directory structure "%windir%\Microsoft.NET\assembly\GAC_32\Mercury.QTP.Agent\v4.0_8.0.137.0__7d38df5e43b1c39a".
7. If QTP_00669 (OR 64bits support patch) is in play, then copy "C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Net4\Mercury.QTP.Agent.dll" to directory structure "%windir%\Microsoft.NET\assembly\GAC_64\Mercury.QTP.Agent\v4.0_8.0.137.0__7d38df5e43b1c39a".
8. If WPF 4.0 support is related, then copy "C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Net4\Mercury.QTP.WpfAgent.dll" under "%windir%\Microsoft.NET\assembly\GAC_MSIL\Mercury.QTP.WpfAgent\v4.0_9.5.1000.0__7d38df5e43b1c39a" /y.
If this doesn’t works then try steps from 9 to 12
9. Open the directory c:\windows\assembly\
10. Check that two files called Mercury.QTP.Agent exist. Process Architecture should indicate AMD64 and a blank value
11. If the assembly with the process architecture of AMD64 is missing, drag and drop the file
C:\Program Files (x86)\HP\QuickTest Professional\bin64\Mercury.QTP.Agent.dll
to
c:\windows\assembly\
12. If the assembly with the process architecture of blank is missing, drag and drop the file
C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Mercury.QTP.Agent.dll
to
c:\windows\assembly\
1) Close QTP and any other application.
2) Open a CMD (command prompt)
3) Navigate the following path on your local file system: <<QuickTest installation folder>>\GlobalAssemblyCache\Net4
4) Execute the following commands:
..\..\bin\GACRegUtil4x86.exe -i Mercury.QTP.Agent.dll
..\..\bin\GACRegUtil4x86.exe -i Mercury.QTP.WpfAgent.dll
5) Check if this works, If no then try steps from 6 to 8.
6) 1. Copy from "C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Net4\Mercury.QTP.Agent.dll" to this directory structure "%windir%\Microsoft.NET\assembly\GAC_32\Mercury.QTP.Agent\v4.0_8.0.137.0__7d38df5e43b1c39a".
7. If QTP_00669 (OR 64bits support patch) is in play, then copy "C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Net4\Mercury.QTP.Agent.dll" to directory structure "%windir%\Microsoft.NET\assembly\GAC_64\Mercury.QTP.Agent\v4.0_8.0.137.0__7d38df5e43b1c39a".
8. If WPF 4.0 support is related, then copy "C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Net4\Mercury.QTP.WpfAgent.dll" under "%windir%\Microsoft.NET\assembly\GAC_MSIL\Mercury.QTP.WpfAgent\v4.0_9.5.1000.0__7d38df5e43b1c39a" /y.
If this doesn’t works then try steps from 9 to 12
9. Open the directory c:\windows\assembly\
10. Check that two files called Mercury.QTP.Agent exist. Process Architecture should indicate AMD64 and a blank value
11. If the assembly with the process architecture of AMD64 is missing, drag and drop the file
C:\Program Files (x86)\HP\QuickTest Professional\bin64\Mercury.QTP.Agent.dll
to
c:\windows\assembly\
12. If the assembly with the process architecture of blank is missing, drag and drop the file
C:\Program Files (x86)\HP\QuickTest Professional\GlobalAssemblyCache\Mercury.QTP.Agent.dll
to
c:\windows\assembly\