It has been many years since the official Yu-Gi-Oh! Power of Chaos pc games were released. Did they release an update or a newer version which I am missing? If yes, where can I download (or purchase) it?
According to the Wiki, Yu-Gi-Oh! Power of Chaos consisted on a series of three games, which were (in order of release):
Seems that there are no further releases of the Power of Chaos series.
As for where to download or buy there are several options, so the best would be to Google the specific release of POC you seek and chose among the options (I also want to refrain from promoting a specific page or product)
A quick search revealed several sites that offer download, and I am sure that you could find it on places like Amazon or EBay