I totally agree with Robert.

BOL 2008 doesn't mention SQL Server 7.0 since mainstream support for 7.0 ended in 2005. So the BOL 2008 doesn't mention it as "side by side supported", since it is not (mainstream) supported anyway!

As BOL2005 mentions it as "side by side supported", I would definitely think it will still run fine side by side with SQL 2008, though it would be nice if anyone could confirm that after testing (I don't have anything on SQL Server 7.0, so I can not do so).

Maybe the question should be reworded to: "what side by side installations are supported", but I'm personally more interested in what's possible than in what's supported.