I've found an AWESOME program that installs Device Hook (DevHook) on your PSP!
Here it is- [-Link Removed-]
It is an exe file, but it's not a virus. If this link is broken. the search for
"UI v1.1.1" exactly like that, including parentheses. This makes google search for the exact phrase. The file should be 20.6 megabytes.
Devhook is a program that you run on your 1.5 firmware psp and it lets you emulate (run a system on another system temporarily) any psp firmware, but only comes with 2.71. DevHook can do any other firmware but you must manually install it to your PSP. This only runs on 1.5 firmware PSPs due to their lack of security capabilities or newer firmware versions with an eboot loader (but what would be the point?).
Since putting DevHook on your psp manually is very difficult for new people (like me), this program is very useful.
YOU HAVE NO CHANCE OF RUINING YOUR PSP USING DEVHOOK
All it does it load the firmware into your PSP's ram. This also means it goes away when you turn off your PSP.
Some of you may be wondering why you would want or have firmware 1.5 anyway. This is because you can run homebrew on it.
So just click the link above to download the file, then plug in your psp (with memory stick) in USB mode and run the program.