Вам поможет reg файл следующего содержания:
 
REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.RDP]
@="RDP.File"

[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File]
@="Remote Desktop Connection"
"AppUserModelId"="Microsoft.Windows.RemoteDesktop"
"EditFlags"=dword:00100000
"FriendlyTypeName"=hex(2):40,25,73,79,73,74,65,6d,72,6f,6f,74,25,5c,73,79,73,\
74,65,6d,33,32,5c,6d,73,74,73,63,2e,65,78,65,2c,2d,34,30,30,34,00
 
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\DefaultIcon]
@=hex(2):25,73,79,73,74,65,6d,72,6f,6f,74,25,5c,73,79,73,74,65,6d,33,32,5c,6d,\
73,74,73,63,2e,65,78,65,00[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell]
@="Connect"[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell\Connect]
@="Connect"
"MUIVerb"=hex(2):40,25,73,79,73,74,65,6d,72,6f,6f,74,25,5c,73,79,73,74,65,6d,\
33,32,5c,6d,73,74,73,63,2e,65,78,65,2c,2d,34,30,30,32,00

[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell\Connect\command]
@="mstsc.exe \"%1\""[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell\Edit]
@="Edit"
"MUIVerb"=hex(2):40,25,73,79,73,74,65,6d,72,6f,6f,74,25,5c,73,79,73,74,65,6d,\
33,32,5c,6d,73,74,73,63,2e,65,78,65,2c,2d,34,30,30,33,00[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell\Edit\command]
@="mstsc.exe -edit \"%1\""[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell\Open]
"Extended"=""
 
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\RDP.File\shell\Open\command]
@=hex(2):22,25,73,79,73,74,65,6d,72,6f,6f,74,25,5c,73,79,73,74,65,6d,33,32,5c,\
6d,73,74,73,63,2e,65,78,65,22,20,22,25,31,22,00a
Это позволяет восстановить файловые ассоциации для RDP