|I didn't realise Adobe Photoshop could burn DVD's - probably because I no longer use it and it is a feature of newer versions.|
DVD-RW burning is usually a process of copy/pasting etc (ie copying files in the usual computer way - normal file handling onto the DVD-RW). With DVD-R you use your "burner program screen" to add picture files to the collection.
DVD-R are more reliable.
You could try another burner program such as "CD Burner XP" which is free. The title is misleading as it does DVD's as well. You have to use its burner screen, not just copy/pasting files onto the DVD.
As for what you may or may not already have on the DVD then it shouldn't be necessary to add any new viewing program, so long as jpg's (which I assume they are) can be viewed from the HD. If they can be viewed there, it should be possible to also view them from the DVD. So, make sure you can open jpg files which are already on the HD.
I therefore doubt that you actually need any new viewer program, such as IrfanView, but I do think it is a nice viewer.
Subject to the above, I still believe that for some reason something went awry with the burning process but it would certainly be worth trying a different brand of DVD. I know it sounds odd but I've been caught that way many times on different computers. Why some are fussy about media brands beats me, but it sure happens.
Have you tried browsing your DVD in some other machine - a friends perhaps?
Long Range Golfer