That did the trick!
Manually downloaded the *.sst files manually and then ran...
updroots authroots.sst
updroots updroots.sst
updroots -l roots.sst
updroots -d delroots.sst
updroots -l -u disallowedcert.sst
Thanks for the input Dave!
Still havent figured out why heinoganda's Cert_Updater 1.6 doesn't run on my XP and there is nothing blocking it? It works fine when tested in W7 and W10...
Anyway, I got the certificates updated on my XP by doing it manually as mentioned above.