How can I troubleshoot a slow DVD writer?

"Sometimes this problem happens because the drive's firmware doesn't recognize the speed capabilities of newer media. You can try identifying your specific DVD device and it's firmware version, and see if you can find a newer firmware for it.

If you have the Nero suite installed, the Nero InfoTool application is useful for identifying device firmware. The laptop or device manufacturer's website would be the best places to look for newer firmware.

You could also try:

Use a different burning tool, like ImgBurn.
Using a different type of media. If it's an older drive, it may burn DVD+R at higher speeds than DVD-R (or vice versa), or it may be incapable of burning dual-layer discs faster than 2x. If you're using single-layer media, try using -R instead of +R, or use a different brand of media. If you're using dual-layer discs, try burning single-layer instead.
Check the Device Manager's entries for the DVD, hard drives, and drive controller. A yellow exclamation mark (!) on an entry indicates a problem.
Shut down all background programs, firewalls and antivirus, in case your burn is suffering from resource starvation by another program or service.
Defragment the drive containing the source files you're trying to burn. If the source files are heavily fragmented, the drive may not be reading fast enough to keep up with the requested burn speed."