Depends. If the game needs Dx7 and it says so in the literature, then by
electing to install the game you are electing by default to install DX7.
Its rather pointless to install a game that needs whatever new version of DX
[or any other API]. However, the installer program SHOULD at least inform
you it needs to install DX version whatever and at least give you the option
of not installing the demo at that time.
But all this whining about DX7 being a malicious virus, "infecting the
system", being installed "without your permission", etc, etc. is the same
tired bs that happens at about every release of DX it seems. Before
complaining, try updating ALL your drivers for audio, video and any other
*** periperhals.
And btw, when you click that "install ok" button in any installer program
you are giving that program your permission to install anything it needs,
period. Try reading all the readme.txt and other information files that
come with a demo or other program to make sure agree for the most part with
what it is installing and the requirements, such as DX7, to run the
software. If you don't agree with any of it, don't install the program.