As the (invisible to non-registered users) entry clearly states (https://www.portablefreeware.com/?id=1707), Album Art Downloader "is NOT actually portable and was added to the database prematurely". As TPFC is an entirely voluntary community, such things tend to happen from time to time. Notwithstanding, I'm moving this topic to 'non-portables'.
BTW, latest AAD version is v1.03, dated 2018-03-07 (changelog is at sourceforge.net /projects/album-art/files/album-art-xui/Changelog.txt).
Apparently, DotNET requirement is now v3.5, according to support thread at https://hydrogenaud.io/index.php/topic,57392.0.html.