Rob and Tim, I think I have found the solution.
Rob - yes, both my PCs can play commercial DVDs and as of today, content from DVD-RW that I have recorded.
Tim - It was the comment you made about recording modes on Pioneer VR and Video mode. I had another look through my manual and it does not list anything on this content, however I was able to download a manual from their website. This indeed does cover information on VR and Video recording modes and most appropriate one to use.
In this case the Video mode is recommended if one wants to view the files on most DVD players and PCs. At the time the disk is inserted, the "Initialise" option under the setup menu must be used. This will provide the option to initialise as VR or Video.
At the end of recording the required content, again from the setup menu: one must choose the "Finalise" option to close out the recording on the disk. Once finalise is chosen, no more content can be written to the disk. Once this step is performed, content can now be viewed on both my PCs. I am yet to test on a DVD+ machine.
Also, as you would expect and most likely are aware of: once the Initialise option is used, it will erase any prior content on the disk, therefore there is no option to change VR recorded content to Video.
A lesson well learnt now.
Rob and Tim, thank you so much for your quick help and suggestions. I really appreciate it.