Monitoring Server Resources with System Monitor - Professional SQL Server 2005 Performance Tuning - page 19

Figure 2-1

Even with a relatively small number of counters it can be difficult to distinguish between counter values.
In Windows Server 2003 there's a toolbar icon showing a lightbulb (which is represented by a pen-shaped
highlighter in Windows Vista). The highlight tool can be used to match counters on the line graph with
the counter selected in the counter list. This can be really useful when handling more than a few counters.
It can also be enabled by pressing Ctrl + H.

The form in which the data is displayed can be changed either using right-click properties or through
the toolbar icon symbolizing a line graph. A bar graph display is available, although this tends to be less
useful than the line graph. Additionally a report view is available that presents data in a numeric form
(see Figure 2-2). This can be useful when monitoring a large number of counters, and can also help ensure
that your interpretation of the data isn't skewed by scale.