First, This is a post explaining why you can not burn a UMD in the real world.
Secondly, it is a post for all those who think it is possible.
Third, if you want to make this a sticky, be my guest.
ecasmb posted in his thread a way to burn UMD's in Dutch. That thread has rightfully been closed. He/she is very wrong about the method that is proposed.
In theory it is possible to burn a UMD. You need a UMD Burner and blank UMD Recordables. And that is where the theory ends. Neither a UMD Burner nor UMD Recordables are available any where on this planet as far it is known.
In theory you could change a existing DVD/CD-burner to burn a UMD, however there is still the problem of the missing UMD Recordables. You have to ask a manufacturer to make those. Without the right connections and money it will never happen. And you need to be very good in working with electronic components to modify a DVD/CD-burner.
As we know a UMD is following the ISO9660 format up to a point. However track 0 starts earlier on a UMD than on a DVD or CD. You can see that by comparing a UMD and DVD/CD.
Therefore it is impossible to use a unmodified DVD/CD-burner to make a UMD.
The UMD will most likely never be read in a PSP.
Well, how about using the UMD Reader in the PSP? The laser build in the UMD Drive isn't strong enough to burn a UMD unless you burn it at a very, very slow speed. But you will need those unavailable UMD Recordables. The UMD Drive used this way will get damaged.
Because there isn't a UMD burner available at the moment, you will only see stamped UMD's. And Sony will never sell games or movies on a UMD Recordable. They will always sell a pressed one. It can ensure a longer lifespan.
If you even get it all managed to make a UMD Burner and get UMD Recordables, you need the encrypted image of a UMD. Currently the only images floating around the internet are the unencrypted ones. You have to make a program that dumps the encrypted image on your memstick in your PSP.
The UMD Drive contains a small firmware (aka microcode) that tells the unit on how to read the UMD's and so on. Currently there isn't information available that the firmware in the UMD Drive is even able to read a UMD Recordable.