System: Sony laptop with a DVD ROM drive/Win98SE

Question 1: I have added an external DVD (Pioneer 104) burner and have
burned a home movie to both a DVD-R and a DVD-RW (same movie). The Pioneer, naturally, will play back both disks correctly. The DVD ROM drive will only play back the DVD-R disk. Is this to be expected? I thought I had read where this is correct but I am not positive.

Question 2: This is a SONY with all of their proprietary software. I use
Media Bar to play my CD's and the commercial DVD's that I have bought.
Somewhere along the line I think one or more of the DVD's installed their
own players...one was InterActual and I forget what the other was but I
preferred Media Bar's player. So, I removed them through the 'control
panel' method and I think their removal somehow messed up my file
associations. I have tried everything to get everything back but so far no
luck. When I insert a DVD (whether commercial or home made) I get a popup window error:
'Windows cannot find program. (Then a blank line) This program is needed for opening files of type 'File'." It then will let you browse to find the file but when I select the Media Bar DVD player, it says "Cannot
find'C:\.....program". No matter what I enter or select, I get the same
response. Can anyone help?

Question 3: I cannot play either the DVD-R (Memorex brand), or the DVD-RW (came with the drive - ESbuy brand) on my stand-alone DVD player (SONY DVP S560D) which is about 3 years old. I took both disks to a local CircuitCity and could NOT get any of their DVD players to read the disks either. I feel as though it is due to the brand (if that is possible) of disk. What brand has shown to be more compatible as far as the DVD-R's are concerned?

Thanks for time and any info.

Bob