Weird problem with DVDs not working on a Laptop

[schotty]

I'm having a problem backing up a couple of movies for a friend. When she plays the original on her Toshiba Laptop the moview work fine. When I copy them for her on a Sony DRU510 External burner on Ritek 1x and 4x DVD-Rs she is unable to play some of the disks.
I've backed up several DVDs for her (probably 5/6) and she has been able to run 2/3 on her Laptop but not 3 of the other ones.
I'm following the same procedure for each of the disks (running DVD Shrink 3.1.7 and burning with Nero (though not the lastest version) I think it's 5.x.

When I tried each of the disks in my laptop, they worked fine.
She was running Windows Me so I thought that that could be a problem, and upgraded her to Win2K, installed all the drivers, upgraded the firmware and tried the disks again, Same thing happened, could play the originals but not the copies of these 3 disks. But she could play the other 3 disks that were backed up.

I've checked the region of the player, as it's set for region 4 but is not locked yet. The disks are all set to region free.

Thanks for your help in advance.

[Imperial Zeppelin]

What type of laptop does she have? I have a 3 year old Dell Latitude that is very picky about backup DVDs, even ones that play fine on my most persnickity set top player. It's especially picky about longer movies; my backups of LOTR are usually not read by this unit.

Zep

[schotty]

She has a Toshiba Satellite Pro 2800.

She's just bought a Stand alone player and they play fine in that.

Grrr at unreliable DVD drives in a Toshiba.

Schotty.

[vfrjim]

I had similar problems on my Laptop and what solved it was that I tried the latest version of Nero and then all the dvd's that I burned played on the laptop.