I was intrigued by your report , so I connected an external HDD in which I had archived a copy of
NDP462-KB3151800-x86-x64-AllOS-ENU.exe
originally downloaded Sep 14th 2016; that off-line installer was dual-signed (SHA1+SHA2) on July 15th 2016;
running that installer now, after file extraction, generates the familiar error below:
I closed that installation attempt and then went to
https://dotnet.microsoft.com/download/dotnet-framework/thank-you/net462-offline-installer
Direct link is
https://go.microsoft.com/fwlink/?linkid=2099468
The latter fetched file
ndp462-kb3151800-x86-x64-allos-enu.exe
(in small letters this time ) which is only SHA-2 signed on May 1st 2021;
my Vista SP2 32-bit system has SHA-2 support installed, so when I ran that second off-line installer, and after file extraction (takes a few seconds, because it scans ALL your drives to choose the one with maximum FREE disk space), I was, surprisingly, presented with:
Now, I didn't click Install to go on with the 4.6.2 installation, because I wasn't yet ready to part with my existing, perfectly working, 4.6.1 setup... Perhaps the 4.6.2 installation would have aborted at a later stage, or perhaps NOT... The thing is the updated .NF462 setup doesn't immediately barf when it detects NT6.0; another kind soul with Vista SP2 in a VM could try that new installer to explore whether it "requires special procedures" to complete the installation...
FWIW, since this revised setup targets WS2008SP2, I expect it would require a special minimum set of WS2008SP2 updates to be present in your Vista SP2 image...