Even though this issue has an official FAQ on this page, I decided to include these short instructions on my blog.

Symptoms

When you click on Disk Performance tab on any disk page, Hard Disk Sentinel says the following:

• Real time performance monitoring is not supported on this disk

Here is how it looks:

Solution

Works for me most of the time (Windows 7 x64):

1. Start cmd as Administrator.
2. Run lodctr /Q to list available performance counters.
3. Scroll up and make sure PerfDisk is Disabled.
4. If it is, run lodctr /E:PerfDisk.
5. Restart Hard Disk Sentinel.

Tested on version 4.20 (latest at the moment of writing).