CDR or CDRW Disks

[Zachary]

Hi,
I am wondering whether it would be possible to physically erase the contents 
of a CD, so as to convert it into a blank one.  I have only 1 cdr disk, 
which is not enough to install Slackware Linux, unless I am mistaken.  I 
just need one more disk, and am wondering whether I can either download a cD 
formatter program, or just have to go out and buy another disk.
I'd rather not do that, as I have plenty of disks already.
Thanks,
Zachary