Sorry Marco, the MSFT_PhysicalDisk class is supported on Windows 8+ and I tested in Windows 7; see my reply to Yousfi message #165673

>Ok.. not knowing about your environment is hard to tell,
>but after reading Doman's comment.. makes sense if you are using
> a vm... other than that.. I've found that detecting ssd seems to be
>something that you can achieve for sure only by getting the hd model
> and looking for it using some kind of service.
>
>If your concern is HDD performance, you can query "Win32_PerfRawData_PerfDisk_LogicalDisk"
> I included it on the sample, and called the object "hdperftest" ( it's commented ) or simply do:
>
>oHDPerformance=wmiquery('Win32_PerfRawData_PerfDisk_LogicalDisk')
>
>to get ( attached image ) performance test for all your logical disks.
>
>( tests can take time 5-10 secs depending of your system ; no message will be shown while wmi query runs )
>
>Marco