I'm an owner of NEC ND-2500A and in Nero, under recorder options, there is an option DVD High compatibility mode (over 1G data).
Why is it used and is it useful??
It means that at least 1GB will be written to the disc. So, for instance, if you make a compilation of only 500MB Nero will add dummy files to make the file size larger than 1GB. This is helpful because some players cannot play DVDs that are smaller than 1GB. The option is useless if you just burn complete DVDs.