I have ripped 2 of my DVD's to my Hdrive using DVD Decrypter.Then use DVD2one then Nero to burn. One will play on my standalone DVD and one won't.Is there a way to check the files,Ive tried with IFOedit and they both look the same but I'm a newbie so I'm probably missing something.

Once the files have gone through dvd2one, open IfoEdit and find the folder where the new files are and run one of the 2 files it shows, then you should be able to tell if it worked fine, might just be the media you used.

Also, make sure you are using the very latest version of Nero (5.5.10.15) as some earlier versions had a problem with compatibility in some standalone players.