[link|http://www.nero.com/en/index.html#c1004534911820|InCD]
[link|http://www.roxio.com/en/products/ecdc/dcdfeatures.jhtml|[link|http://www.roxio.com/en/products/ecdc/dcdfaqs.jhtml|http://www.roxio.co...cdfaqs.jhtml]]
[link|http://www.stompinc.com/recordnowmax/rnmx-retail.phtml?stp|Veritas DLA]
These programs let you use a CD-RW disk as if it were just another read-write drive letter.
All are bundled with other CD burning software to varying degrees. There are also free read-only drivers out there (or built into WinXP and I think W2K) for the supposedly standard UDF format they use.
I can't vouch for the reliability of this option, I'm only just now looking into it myself. I've seen many reports of compatibility problems between programs and versions while trawling Google Groups for info.