Performance Monitor limits its' reporting percentage to 100%.
Some performance counters, like Physical Disk / TOTAL can exceed 100% when multiple drives exist.
Starting with SP3, the CapPercentsAt100 registry value allows reporting of percentages above 100%. Navigate to:
Add Value name CapPercentsAt100, a type REG_DWORD value, and set the data value to 0. The default is 1, which limits the results to 100%.
NOTE: If the PerMon key does not exist, run Perfmon to create it.