I haven't used monitor solution in 6.x, but I'm guessing you need to join the vMonitorData table to a different table using the GUID. The different table, of course, will include the max CPU speed for that system -- which Altiris has matched by using the GUID.
select top 10 [owner] [Owner Name], sum(cpu) [CPU Usage Total] from vmonitorprocessdata
JOIN Inv_AeX_HW_CPU ON Inv_AeX_HW_CPU.MachineGuid = vMonitorProcessData.MachineGuid
where [owner] not in (
'system',
'root',
'network service',
'administrator',
'local service')
group by [owner]
order by [CPU Usage Total] desc
This is approximate -- dive into the DB for details. This would work for a single CPU system, anyway -- might need additional tweaking to add up total CPU capacity for a system with multiple CPUs. But right here you could do
[vMonitorProcessData].[CPU Usage Total] / [Inv_AeX_HW_CPU].[Speed]