minor doc issue

[eliliang]

minor documentation issue:

Those people who are running Vista won't be able to use "menu:Help->Contents" from within HCE unless they have first downloaded the WinHlp32.exe from Microsoft:
Microsoft WinHlp32.exe This is because HCE ships with the old help file format no longer used on Vista.

This should probably be mentioned in either Section 5.7 (p.55) of the Manual or in the Release Notes.