I assume that you mean buffer underruns.
This is when the CD is writing faster than the data comming to it.
Are you copying CDs?
If so, you either need to reduce the speed, or re-configure your system so that both drives are not on the same IDEchannel.
4X to 8X is about the fastest you can copy CDs on the same IDE channel.
Next, what software are you using?
Some of the newer software packages include buffer underrun protection.
They slow down the burner so that the buffer remains full.
I have a HP 8200 series on my Athlon 750 System, and have to close down everthing using Alt-Ctrl-Del to show a few hidden applications.
Also, how much free hard drive space do you have?
You want to have at least 1GB free space when burning. (Even if you are not saving to disk)
Finally, do you have virtual memory set to a small fixed size?
This can also cause probelms.
Chas