You can't turn off the SmartBurn running laser calibration and speed control. When you uncheck SmartBurn in Nero, you are only turning off the initial speed limitations. Trust me, the drive is saving you from a coaster. Your media is just not up to high-speed burning. It may also be that your drive is unable to calibrate the laser properly for the higher speeds, O/cing 40x drives is not always successful in that regard. but you are not using decent high-speed media, so you can't tell which it is. Suggest you review the SmartBurn functions and how they work.
Users always want to successfully burn a disc with a higher speed in CD-RW drive. You may know, there are so many brands of CD-R / CD-RW media in the market with irregular quality & still being cost down in the price war.
LITE-ON IT try hard to collect various kinds of media to come out the dedicated optimized writing strategy parameters plus the outstanding running Optimum Power Calibration ( OPC ) function to provide you the best burning quality.
If your CD-R / CD-RW media quality is really poor enough or working environment is too hot to induce the Laser Power over margin, the CD-RW drive detected, the burning speed will be forced to decrease to get more reliable Laser working power to secure the life of CD-RW drive & burning quality.
The buffer under run error is also no longer happened to your drive anymore, SMART-BURN also can allow drive to be suspended during writing, than continue to burn from last point when enough data get in the buffer.
SMART-BURN features :
Buffer Under Run Error Free
Running Optimum Power Calibration
Automatic Writing Strategy & Burning Parameters
Automatically decrease burning speed when Laser power over margin due to poor media quality or high temperature