DVD/+R+RW problems….Won’t play DVD’s

Hello, I purchased a 16xDVD+R+RW Double layer Burner. I can get it to play music cd’s and burn cd’s but not play DVD’s. Also XP crashes when I run some of the burner programs which I read would happen if the proper driver was not installed. When I try to install it, XP crashes again. I am using Nero 6 software which includes the decoder. Windows Media wants to default in and will not read Neros decoder and informs me not to use it with Windows Media. I would like to know how I can override Windows Media and also get the DVD’s to play. I also kept my old dvd burner in as an extra cd rom. I have both hooked up as slaves just like they were when I changed them out. I’ve installed, uninstalled and reinstalled and still the same. Thank you for any advice you can give me. Cindy