Moved this to help.
Just upgrade to 2.71, then downgrade using this tutorial:
http://www.pspbrew.com/forum/viewtopic.php?t=6810
Once you back at 1.5 just upgrade to a custom firmware, the 2 most used are 3.03OE-C or 3.40OE-A.
Here is a winstaller for 3.03OE-C:
http://forums.afterdawn.com/thread_view.cfm/460892
And here is a winstaller for 3.40OE-A:
http://forums.afterdawn.com/thread_view.cfm/500493
Then you can use our brew pack generator or downloads section to download the latest nes and snes emulators. Then put them in your GAME folder along with the ROMs in the emulators folder. Once you have done that then you can completely turn off the psp, and turn it on while holding the R button. This will make your psp go into recovery mode. Then go to configuration and change the Homebrew folder kernal to 1.50.
Or you can put the emulators and ROMs in the GAME150 folder if you decide to reformat your memory card after the upgrade process is complete.
Ok I believe that raps it up. Ask if you have any more questions.