mod chips can be tricky. i toasted a PS2 modding it once. that was uncool. i fixed my dillema in the end via means i will not divulge. the point being that you best be prepared to lose the ps2 if your going into soldering. if your going into the plug kind then your moderatly ok but your still out your warrenty. the best solution thus far? the ps2 slim jim (for lack of a better word) basically you got 1 boot disc and a slim jim. you boot the ps2 with the disc and then used the slimjim to open the drive door to swap the disc. by doing this without pushing the eject button the ps2 never knows that the disc was swaped and therefore does not reset the code it just got. you can get the slimjim and the boot discs in one package from here:
http://www.consolesource.com/playsta...p2-sld-msw.htm
this is where i usually get my junk. they are damn nice people.