In an article I posted last December, I bemoaned the lack of WinHlp32.exe in Vista. At that time the updated Winhlp32.exe was not available. This was described in KB 917607.
Re-visiting the KB - and an updated version of WinHlp32 is now available. This provides a version of WInHlp32.exe for both 32-bit and 64-bit versions of Vista. Installing the update brings back support for older Windows help files.