Burner not burning close to 16x

When I burn a dvd the disc only burns at around 5x but I use 16x drives. I use a nec 3540a and a memorex to read it(no comments). I have the latest drivers for the nec and im using alcohol 120 or nero retail. My specs are as shown:

A64 3000+
1Gb corsair valueselect
120 maxtor harddrive.

Im also doing copy disc to do it. I know that doing it off the hard drive is faster but Im waiting for a larger hard drive. Thanks for the help : )