I had no idea that Nero was supposed to recognize them... I've been burning them (overburning, according to Nero) for years now, with no problems. I dunno, as long as you know how much the disk can hold, you can override Nero and burn them perfectly fine. 800mb disks aren't technically following the CD standard, so I guess they cause problems because of that. The tracks are slightly closer together than normal CDs. Anyway, I'd just remember which disks are 800mb, and force Nero to burn them that way.