XP for example does not include a DVD (video) player. Look up VLC PLAYER to fix that.
For DATA DVDs there are some dozen DVD recording softwares that use DVDRW media like a big floppy drive. All versions of Windows would have issues with that so think back and see if a name like Nero, Roxio, Adaptec, GEAR... HECK, read http://en.wikipedia.org/wiki/Category:Windows_CD/DVD_writing_software
I just completely wiped my computer and started over. I got my drivers back, but for some reason my DVD-ROM only reads CDs, and not DVDs. This is weird, since before the wipe it read both, and my computer still says it's a DVD drive. It appears to be installed and "up-to-date," but I can't get it to even recognize DVDs. How can I fix this?