Problem playing DVD-RW on computer

[basss]

I have tried some attempts to make a DVD now, but I am having problem playing the DVD I make on my computer. I have also tried on a Powerbook with Apple DVD player. Both on the PC running Windows XP and on the Mac I can open folder view. I have had success with one DVD player on the PC: PowerDVD. Sonic Cineplayer and Windows Mediaplayer won't play the DVD. With Cineplayer I can open the DVD when I write it to a folder on the Harddrive, but not when try to read the DVD. I have also had success playing the DVD on PS2. What is wrong? I wan't to make some DVDs for gifts for my family this christmas, so it is not good enough that it is working with PowerDVD as long as other programs don't work.
I've tried several different authoring programs, so it doesn't seem to be the authoring program either.
Please help!

---------
Asus A7V133 - Duron 1300 - 512MB RAM - Matrox G450 - Soundblaster Audigy - Canopus DVRaptor - 2x Maxtor 60GB HDs - Pioneer DVR-A05

[basss]

Should I try writing a DVD-R and see if that works better?
Have noone had the same problem with playback on PC?

[basss]

I tried burning to DVD-R now and it seems like CinePlayer 1.5 plays DVD-R fine. Windows Mediaplayer also plays the DVD-R.
But I still find it a bit strange that CinePlayer and Windows Mediaplayer won’t play DVD-RW, while WinDVD and PowerDVD does.
I also tried doing a clean install of Windows 2000 on my second Harddrive, but with no better success there.. I got this errormessage in CinePlayer when trying to play the DVD-RW: “The DVD key exchange for copy protection has failed. Playback is not possible”.
I tried the DVD-R under Windows 2000 as well, and it plays without problems.
Is it something wrong with my DVD-RW disk?