You need Avast 18.5, which was the last version for XP/Vista.
Filepuma no linger lists that file.
@bob3160 has a copy of XP version that he shares. See this post for link: End of support for Windows XP/Vista - #283 by bob3160
Note that it may show as “you are unprotected” as the free licence expires (but should not do that). The virus defs seem to update OK but Avast have warned they do no testing on XP anymore. Ref: End of support for Windows XP/Vista - #317 by lukas.hasik