Zip disk space availability question

Need assistance here, I'm trying to fill up the available space on my new zip disk. I'm trying to transfer tons of drum samples that I have on CD Rom to zip using a PC, I have a iomega 100 ext parallel zip drive that I'm using for the transfer. The problem is that I'm only using up 25% of the disk space to the point where I can't transfer anything else. I bought 3 new iomega zip 100 disk and started the process, didn't format them or nothin since I was told that there was no need to, especially since i'm running xp on my PC when I have a 2000xl, heard that 2000xl was built on windows 98 software? Anyway, load what I was able to transfer to the MPC 2kxl and everything is fine but for some reason I can still save a little bit more data on the xl with additional samples. I check the disk space on the PC and there is plenty of room left. Can anyone provide an explanationn / solution? I wish to fill up the avaliable space.
Thank you Very much

Do you use folders?

no, I don't use folders when i transfer the data but the CD Rom is filled with folders that's labeled with different drum kits. All I do is open each folder and highlight the drums and transfer it to the zip drive, unless there should be a different way I should follow.

Well there is the answer to your problem. Create a separate folder for every project/beat you make and save all data related to that project/beat in that folder. Don't write any data in the rootfolder of your zip disk.