psp umd region code problems >.<

I have a JP psp imported back before 2.0 and up untill now ive only used it for homebrew and like 2 umd games

long story short

i recently recieved a usa umd of doom and got this error
(game could not be started, regioncode incorrect)

my jp psp runs us games AND jp games no problem but i was wondering if there is a way to check my psp regioncode? i know its jp but i thought the old jp psp's were any region

what i mean is how can i find out what codes it can run (1,2,3 or 1,2 or just 1, 2 OR 3)

or if there has been a program to allow regioncode override on movies a link would be cool

im lazy.... it happens

id greatly appreciate any help thx

if you have jap 2.0 u need to downgrade with a u.s. firmware 1.50 then check if it work
it work for me!!!!! and if u want upgrade back 2.00 make sure it a u.s. 2.0 firmware
p.s. pm me and tell me it work