I've got a psone, unmodded and I just use the item below. It works with ALL ddr games i've got (about 6 dif ones).
http://www.divineo.co.uk/cgi-bin/div-uk/uk-psx-xchge
Just pop the cd in, wait until it asks you to swap for the import, then hit x.
Simple as that. U won't need any codes or modcartidge etc. Just the disk.
Hope this helps,
J