Not having your hard drive defragged shouldn't prevent you from burning or effect it but it does. The reason is that dvd burning goes smoothest when it has a constant flow of data without slowdowns or interuptions. Its the same thing for spyware. It wont directlly interfere with burning, but franky, dvd burning requires a lot of system resources and speed, and the smoother your system is running, the better the burn. If anything is tying up your systems resources or slowing it down (especially if your computer is not the fastest), it could effect burning. Same thing goes for having too many programs running. If your system runs out of phisical memory and starts heavilly relying on page files (which usally slows the system way down), that too can influence the quality of a burn. In fact, if it cannot supply data fast enough during a burn that the buffer runs out, it can cause it to fail or it may just cause a bad burn. I get the impression that some drives can slow down the burning if data is not coming fast enough, like for instance when you try to burn at 16x in pio mode, since the drive cannot get data fast enough, the drive must slow down the burn. Since you are not allowing the drive to follow the write strategy properlly, it can still finish the burn soemtimes, but the burn quality becomes a crap shoot. I learned this the hard way when my computer was set to pio mode and didn't realize this. I didn't figure out that it was in pio mode till I started trying to do cdspeed transfer rate tests that would not go higher than 10x, and it explained some problems that I was having.