Panasonic DMR-EZ27EB - using DVD's on other DVD readers and/or pc

I bought the above DVD recorder 9 months ago - the idea was to keep ahead of the demise of VCRs. Since then I have copied scores of VCR-based material onto DVDs with no problems.

..until I tried to play a DVD on the pc via the PowerDVD software - it does not work. I read the manual and found some reference to 'finalising' the DVD before it can be used on other players..only to find that the DVD Management section of the Function Menu does not display 'Finalise' ...

The local Panasonic dealer tells me that I am using the wrong DVDs - despite him selling them to me in the first place.. these are Panasonic DVD-RAM (non-cartridge 3x speed) - the proferred solutions are (1) record all the VHS again - onto the 'right' DVD (2) buy a new DVD player with a hard drive..copy the DVDs to HD then burn them onto the 'right' DVD
Option (1) is no good as I no longer have the VHS's and (2) is unrealistic - a cost of £280 for a new unit.

I've asked PowerDVD for a solution but they need to know the file format that is used when the Panasonic recorder burns the DVD .. if I place the DVD into the pc DVD reader there is nothing shown - no title, no evidence of the programme on the DVD (even though it is certainly there).

Is there a cost-effective solution to this problem?
What is the file format type that Panasonic-burnt DVDs use?

Any advice greatly appreciated