I've had this Lite On DVD writer for a little while now and this same problem consistently. But I just don't get whats going wrong.
It seems to burn discs fine but then when I try to use them in another DVD Drive or Cd Drive they just can't be read. So far I havent bothered about it much since I've mostly used it to back things up for my own pc. But it really gets to me when I try to burn a disc for a freind or family member and they get it home and its no good. Video CD's or SVCD's etc work ok in DVD players, and I've burned MP3 cd's that work in my HI-FI. This problem only surfaces with data discs.
If anyone has any ideas what could be wrong with the drive or maybe some mistake I'm making please help. I've been burning discs casualy for years now and this is the first time I've had this issue. I thought I had it down, but I dunno, this really has me stumped.
The drive code is DH-20A1P-45C.
I use Nero 8 for burning.

Make sure you close the disk after burning data disks so that nothing more can be added to them. There will be such an option in the Nero configuration just prior to burning. Disks that haven't been closed are generally readable by the drive that has partially burned to some of the space but other drives may not be able to see the contents until "closed". I'm pretty sure you can also go back and close an already still open disk but not sure where those settings would be. If you can't find it just burn one more session with a single small file and ensure closing has been enabled. At the disk level it's not to do with the data itself but how it's table of contents is accessed. The TOC only becomes standard and globally accessible after a data disk has been closed.

Thanks for your detailed response Paul it has helped me to understand more about burning discs. When creating a disc I have the option ''Finalize Disc ( No further writing possible)'' ticked, I'm assuming after reading you post, this means the same thing as ''closing the disc''. Please let me know if I'm wrong about that. Unfortunately even with this option ticked data discs are still only being read by the writer :(

There is never total cross-compatibility between all drives and all media. Newer drives are gerally better at reading CDs made by another recorder than older ones. CD drives usually are better than DVD drives due to the colour of the laser and CDR better at being read than CDRW. No absolutes. Using high quality (eg "gold") media helps as does closing/finalising a multi-session disk.

More info (http://en.wikipedia.org/wiki/CD-R).

One other thought is that if one formats the disks (used to have to be CDRW with Nero) for packet-writing (allowing drag and drop from explorer) then InCD (for Nero) or similar must be installed on the PC attempting to read the disks.