In the SDK 10.4.1.1 folder ..system\, the SystemDrivers readme file indicates:
Before using the examples for USB devices, kernel
drivers must be installed. This is normally performed
by the PicoScope or PicoLog installer.
In order to install kernel drivers manually run dpinst.exe
which can be found in one of the subfolders.
For x86 you will also need to copy picopp.inf to SYSTEMROOT\inf
and picopp.sys to SYSTEMROOT\system32\drivers.
Running DPinst.exe seems to have no effect. There is also no trace of picopp.inf and picopp.sys in this SDK version: no picopp folder anywhere. I worked before with SDK 10.1.0.17 and it had a picopp folder...