CAN VIEW THE DVD ON A COMPUTER OR THE DVD RECORDER BUT NOT ON DVDS PLAYERS BOUGHT BEEFORE THE RECORDER

This is quite common of older players. Some only work with DVD+R discs and others with DVD-R discs.
Some player also does not read recordable discs (an early form to try prevent piracy)
Also make sure if recorded on your Recorder, that the disc is finalized before you try to play it on an older player. (See your menu / manual on the recorder for the procedure)

I attempted to play a DVD, DVD-R that I recorded on the Sony RDR-VX515. No problem I played it back on the same device and it had the video that I recorded. However,
when I tried to play it back in my computers, Acer Aspire 4520 and HP Work Station XXW 8200. It loaded it but will not open it to play it back. I don't know
why this happened. I thought that it process was finished in the Sony recorder. Does anyone know the file extension of the video that is recorded from the Sony RDR-VX515?