CheckRedistributableFull.nsi

!define MSVS_DIR "d:\MSVS2010"

;Request application privileges for Windows Vista, 7, 8
RequestExecutionLevel admin 

...

Section "MyApp" MyApp

SetOutPath "$INSTDIR"

;Check if we have redistributable installed
Call  CheckRedistributableInstalled
Pop $R0

${If} $R0 == "Error"
  File "${MSVS_DIR}\vcredist_x86.exe" 	
  ExecWait '"$INSTDIR\vcredist_x86.exe"  /passive /norestart'	
${EndIf}

;do other stuff

SectionEnd

...

Function CheckRedistributableInstalled

  ;{F0C3E5D1-1ADE-321E-8167-68EF0DE699A5} - msvs2010 sp1
  
  Push $R0
  ClearErrors
   
  ;try to read Version subkey to R0
  ReadRegDword $R0 HKLM "SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F0C3E5D1-1ADE-321E-8167-68EF0DE699A5}" "Version"

  ;was there error or not?
  IfErrors 0 NoErrors
   
  ;error occured, copy "Error" to R0
  StrCpy $R0 "Error"

  NoErrors:
  
    Exch $R0 
FunctionEnd