HDCP over DVI is hit or miss. In this case, it's likely that his monitor (which I think came out around 2005), is missing HDCP support.
don't buy a new monitor unless you want something better (HDCP isn't enough of a reason IMO). just get something that removes HDCP like anydvdHD or others (1 or 2 free ones i'm sure).
blu ray is simple on PC, given you remove HDCP
He could simply use the monitor's D-SUB connector. No HDCP at all there since it's analog.