There are four methods which allow you to use almost ANY PlayStation CD in ANY PlayStation, regardless of origin (see below for exceptions.)
The "best" method would be to open your Playstation and hard-wire a switch which would allow you to toggle the lid sensor open and closed plus another switch to allow you to stop and start the CD motor when required. Needless to say this would invalidate your warranty and I do not have the necessary details anyway so this is not covered in the FAQ.
The three remaining methods are detailed below (one safe and two dodgy.)
METHOD ONE: The Audio Menu [Safe and very easy]
Works on : Early Japanese, European and American machines.
Success : 80% Music is often corrupted. Mortal Kombat 3 and Winning Eleven do not work at all. The TOC (Table of Contents) from the boot CD is always used.
o Power up your PlayStation WITHOUT a game or demo CD in it.
o Select the CD Audio menu.
o Get a local CD that matches the country of the machine you have. (ie a Japanese game for a Japanese PlayStation etc.)
o Find some tape, Blu-Tak or something similar. Several people I know have found the corner from a cornflake packet works well .
o Open the lid and look at the top right of the bottom section, near where the hinge is. See the small circle in the groove? Good. This is the lid sensor.
o Insert your local CD.
o Put the tape, Blu-Tak or whatever over the sensor and *gently* push it down. The CD will now spin for a few seconds.
o When the CD has finished spinning take it out and replace it with the foreign game you wish to play.
o Now shut the lid and exit the CD Audio menu. The game should now work fine (see above for exceptions.)
o When you have finished playing, open the lid and remove the tape, Blu-Tak etc from the sensor. This will stop the CD.
Try and get a local CD with as many tracks on it as you can. The local CD must have at least as many tracks as the foreign CD or you won't get all the music. Depending on the boot CD the foreign game may give poor results or even crash.
Unfortunately the number of tracks is NOT the only deciding factor and you may find that you are unable to get your foreign game to work satisfactorily with the choice of boot CDs you have. See the other two methods, they may give better results.
Rayman seems to break ALL the rules and works fine no matter what boot CD you use. Possibly the original TOC is overwritten by the game for some reason?
Striker '96 [PAL] also causes some fatal problems when you try to use it on SOME Japanese PlayStations (using the original Japanese joypads.) The game simply locks up. Problems have also been reported with UK machines when attempting to play with two human players -- more info when I have it.
ii Owners of Japanese SCPH-1000 (later batch), SCPH-3000 machines and the latest European/US models will find that this method does NOT work. Sony has removed this particular loophole.
iii You can ONLY run PAL games on NTSC machines if you have an RGB cable (not s-video, composite or ANYTHING else.) This also applies to NTSC games on a PAL machine. In Europe this problem is easily solved by investing in an import spec RGB/SCART cable as sold for use with Japanese/US PlayStations. In North America, Australia etc you will need to look into the options available to you (an old or expensive monitor, probably.)
METHOD TWO: The Black Method [Fairly safe and easy]
Works on : All machines so far produced.
Success : 95% Most games will work (not Mortal Kombat 3) albeit with with music glitches.
o Follow the Audio method with a local CD in your machine. The lid should be up and the lid sensor held down.
o When the black PlayStation appears (after the white Sony one) QUICKLY lift the original game out and replace with the foreign one. You have a few seconds to do this and it soon becomes second nature.
o If you must have the music working 100% or have a really stubborn foreign game then try the White method detailed below.
METHOD THREE: The White Method [Fairly safe but tricky]
Works on : The same early models that can do the Audio method.
Success : 100% Works with every title I've seen, provided your machine is capable. Required for Mortal Kombat 3.
o Switch on you machine and count 1..2..3..4 and THEN swap discs. You need to do this *JUST* before the white Sony screen appears. The timing is tough, you want the PS to read the country code but NOT the TOC so don't expect to get it right every time.