In XP WPI sets a registry key "LowRiskFileTypes" which tells XP (Outlook, actually) what file types are not dangerous.

Does Vista need this? From what I could tell it does. Someone verify this...?...?

Could you say what this is needed for in XP and WPI?

I use WPI in Vista since one year now and have got no problems.

In XP, a simple window would pop up asking to run this program or not (.exe) much like UAC does in Vista. Thi reg key WPI set temporarily would by-pass the check so installs would not be interrupted.

Kels told me that it is not necessary in Vista, that sources folder and UAC take care of it.