Horace has pointed you to some good places to research making your psp capable of running emulators like pspuae. basically you have an official sony firmware on your psp, you need a custom firmware (hacked version)
the best way is to get someone who's familiar with installing a custom firmware on a psp to do it for you.
if your rich or want it enough, you could buy a psp that has already had a custom firmware installed for you, it's not going to cost you more than 150.00 pounds sterling, or your being robbed!
Or - by getting yourself a pandora battery and magic memorystick, like these here:
http://www.logictoyz.com/sony-psp/sony-psp-2000/psp-2000-modding.htmlthen you can do it yourself, but please make sure you know what your doing before you even try it, people here cant and wont be held responsible for anybody screwing up there beloved psp's
Good luck
I recommend registering on the forums here:
http://forums.exophase.com/then start your research here:
http://forums.exophase.com/showthread.php?t=6832they can help you if your stuck, just post your questions if your not sure what to do