trancexx is correct.
On x64 Vista and Windows 7, file system redirection redirects calls to the system32 folder by 32-bit programs to the syswow64 folder, but there is no 32-bit version of System Restore (rstrui.exe) in the syswow64 folder. You can use the code below to temporarily disable File System Redirection while you make the call.
If @OSArch = "X64" Then
Local $stOldVal = DllStructCreate("dword")
DllCall("kernel32.dll", "int", "Wow64DisableWow64FsRedirection", "ptr", DllStructGetPtr($stOldVal))
ShellExecute (@WindowsDir & "\System32\rstrui.exe")
DllCall("kernel32.dll", "int", "Wow64RevertWow64FsRedirection", "ptr", DllStructGetPtr($stOldVal))
Else
ShellExecute (@WindowsDir & "\System32\rstrui.exe")
EndIf