First, download the following files:
Run the windows Application and let it install everything. If you get asked about unsigned drivers, say OK.
Extract the Zip file and copy the PSPdisp_v0.1\bin\psp\PSP\GAME\PSPdisp folder into the PSP\GAME folder of your memory stick.
On the PSP, plug in a USB cable to your computer and run the PSPdisp application.
On the PC, run the PSPDisp application.
Right click on your desktop, select “Properties” and go to the “Settings” tab.
Select the new display and click the “Extend my Windows desktop onto this monitor” option.
Viola! You should now be able to use your PSP as a secondary display.