Method 1: You can first go to
http://www.gofoxy.net/home/index.shtml to download the FOXY programme, when you have downloaded, you open it and click the "run" button, then, it will be start to setup the FOXY, after the setup, you can click the foxy icon that on the decktop.
Next, you can see the foxy run, if you can't see, you can look at the Right-down corner, then, you right-click the icon and then, in the box, there is a line written: 還原, you click on it. Then it will be open, on the top of FOXY, it have a line for you to write things, on it,you can enter the PSP's game name, it will find it for u, very easy!!!! =)
*****but this programme may be 犯法, so use or don't use is up to you!!!******
Method 2 : wich that this websit can help u:
http://www.uwants.com/forumdisplay.php?fid=905
In fact, download games in the website is not really good, so I suggest you to buy the real one is better!!!!! : )