No. If the disc hasn't been closed/finalized, it may be possible to use the unwritten space (if there is any left) but that's the best you can do. If you want to rewrite discs, you should use the rewriteable kind of discs (CD-RW).
Agreed.... as an almost absolute rule CDRs cant be rewritten (although I have had some freak incidents where i was able to) The key word is "freak"
