can somebody please talk me through what i need to do to get an ISO to play from the memory stick on a psp with firmware 2.71.
thanks in advance

If you do not have a PSP with a TA-082 motherboard you should consider downgrading to 1.50 and installing 2.71 SE to play ISOs.

If you do have a PSP with a TA-082 motherboard, you need to install Homebrew Enabler (Revision C) and use DevHook for 2.71.
There is a package (including a guide) here: http://www.psp-hacks.com/file/821

i tryed to downgrade to 1.5 and i did what the readme file said but when i went to run the program it said there is no need to update. What do i do?
P.S mine is TA-081

Which readme file?
The easiest way to downgrade to 1.50 from 2.71 is to install Homebrew Enabler (Revision C) and run Update Flasher with the 1.50 EBOOT file.
Homebrew Enabler (Revision C) and Update Flasher (Generic Downgrader): http://dax.lan.st/
1.50 EBOOT (Official Update) file: http://www.psp-hacks.com/file/4
Follow the instructions in the Homebrew Enabler and Update Flasher readmes.

i did what the homebrew said in its readme and the color changed like it said it would and then i tried to do what the flash updater said in the readme but when i go to the file that says update XY under the game XMB it says the game could not be started. have i done something wrong or not? what do i do?

I downgraded mine yesterday!!! im so happy...
i used this .exe file (should be on this website)
and it worked for me took like 15min. and quick and easy.
i think the easiest way possible.

i don't understand why this doesn't work i have done everything in the readme files but still doesn't work

well if u make enough posts u could probably download this
if not search Easy 2.71 Downgrader it should just be a program that ends with .exe (remember download from sites you trust)

thanks Dudesweet i downgraded to 1.5 but does this mean i won't be able to use the internet? If you can please tell me how. Also what do have have to do now to get ISOs to work?
Thanks

The easiest way to be able to play ISOs and use the internet is to install Dark_AleX's 2.71 SE:
http://www.psp-spot.com/forums/index.php?showtopic=29545

It's a custom firmware that has all the features of 2.71 but also lets you play ISOs via the XMB.

thanks is works great now