Internet through your mains.

y u no get better modem. lol

Obviously his modem isn't the problem or his PC would be crapping out too, since both his wifi and his bpl are coming from the same modem.

Even if he replaced his wireless router there's no guarantee he'd see any improvement since all WiFi has limitations in regards to distance and degradation.

The best you could ask him is why he isn't using a range extender or repeater, but since he already pointed out his main interest in the BPL is because his computer doesn't have a WiFi card anyway the point is rather moot. He could however take advantage of his BPL as long he got one with more than one ethernet port and install a repeater there at the PC so the WiFi distributes better for the things that can actually use it.