PSP can not read any game after updated

i got a PSP slim 2000
b4 i update, it is version 5.00 M33
n yesterday , i update my PSP system software to Version 5.50
After that, my psp can not read any game. all those old game or new game tat i played b4 also can not read anymore..

any pro here can help me to solve this problem pls..

PS: my psp can't even see the game after i update

thank u

i try to download from here
http://www.us.playstation.com/support/syst...tes/psp/pc.html
version 6.20
but still can not play.. omg.. damn
who can help me?
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UMD is the psp game cd ar?
i don;t hav o.. then how?

i think mayb is my psp don;t hav the M33 anymore.. can anyone teach me how to update back to the version tat got M33 pls...?

then how? how to make my psp got M33 again?