How do you know which version of Pixelshader you have?

Press Windows and the R button together (Win+R) as that opens the run command box and type "msinfo32" as that will open a dialog box with all of your system's information on it.

Alternate: Press (Win+R) and type "devmgmt.msc" in the run command box as that will open the device manager box and will also show all of your system's information.