do you mean your CDRW drive or normal CD-ROM drive?
If you mean CD-ROM drive then it will alwaz default at top speed 1st & if it cant read the CD it will slow down until it can.
If you mean the cache, then ou want to go into performace options under hardware. (right clcik on "My Computer" pick properties.
If you DO mean your CDRW drive, then right click on the drive in Explorer and pick CD Recorder tab, then you can adjust any available options.