Windows update breaks .NET 2.0

The problem I ran into is that the Windows update breaks the .NET 2.0
(atleast). I tried this couple of times (explanation below) in order to find
out when it happened.

1. Clean install to a Thinkpad T61p (formatted HD). Install Vista Ultimate
English ed
2. Run sfc /scannow --> all ok
3. Run Windows update and install all the recommended upgrades
4. run sfc /scannow --> problems which can not be corrected.

I do not know exactly how it was corrupted, but for example installation of
SQL Server 2005 Sp2 express edition fails because of corrupted .NET 2.0.

So, how do I get around this and manage to get a working installation.