Should be something like this:
SELECT dbo.tblComputers.Computername, dbo.tblRegistry.Valuename, dbo.tblRegistry.Value, dbo.tblRegistry.Lastchanged
FROM dbo.tblRegistry INNER JOIN
dbo.tblComputers ON dbo.tblRegistry.Computername = dbo.tblComputers.Computername
WHERE (dbo.tblRegistry.Valuename = 'Start')