As of version 1.4.0 and later, the TortoiseSVN installer doesn't provide
the user with the option to set the
anymore, since that caused many problems and confusion for users who
always install everything no matter whether they know
what it is for.
But that option is only hidden for the user. You still can force the
TortoiseSVN installer to set that environment variable by setting the
property to TRUE. For example, you can start the installer like this:
msiexec /i TortoiseSVN-1.4.0.msi ASPDOTNETHACK=TRUE
Please note that this hack is only necessary if you're still using VS.NET2002. All later versions of Visual Studio do not require this hack to be activated! So unless you're using that ancient tool, DO NOT USE THIS!