How to install Delphi 7 on Vista

Question

I tried to install Delphi 7 on Vista several times and Vista prevented me from doing so by telling me that there are known problems with this application (Delphi 7). Several other people in my company experienced problems with installing D7 on Vista.

This lead to the conclusion that we were at risk with our D7 application, as the company could within the lifetime of the app switch to Vista or Windows 7 and newer Delphi versions are not in the policy of the company. Therefore management decided on rewriting the app in C#.

My question(s):

1. How to install D7 on Vista
2. Experience with such an installation
3. Risk assessment concerning stability of IDE and developed programs
4. Risk assessment concerning executability under Windows 7

Not using any third party components or database - there should be no problem running the developed app under Vista. If not able to develop and debug under Vista (which at the point being will be the only customer platform, yes, internal programming) will result in a sort of cross platform development - if we would be allowed to keep XP as the development platform.

It is not a developers decision to rewrite, it has been done in the company for the last 3 years: if you had to significantly touch an app developed in Delphi or if there was a certain risk of it not to survive the planned life circle/life span, it had to be rewritten. The life cycle just expanded to 2015 due to canceling another project.

So the main issue here would really be: I would like to have educated arguments about the risks.