question about psp OS [operateing system]

Ok i have seen in youtube videos and other videos that people have changed the way there psp OS is, like instead of having an icon bar that is horizontal at the top of the screen from were you choose you music, videos, games ect. it is top to bottom like an ipod's OS runs? how is this possible and can i put this onto my psp with out downgradeing?

Are you talking about XMB Themes? If you are there is a whole section on this site: http://www.pspbrew.com/forum/viewforum.php?f=68

And no, to my knowledge to get any kind of custom XMBs running on your PSP you need to install custom firmware on it...

yes that would be it, the XMB themes ^.^ thank you, so i do need to install custom firmware for them?

To my knowledge yes you do...
Unless you get this other wierd flashless stuff...
but I would just install custom firmware...