If you do not care some special feature like subtitle of DVD

you can compress one DVD with MPEG4 and write it into one CD-R. First you need a tool to rip DVD movie from DVD-ROM and then compress it with MPEG4 encoder. You can choose compression ratio to fit them into CD-R. But the CD-R needs MPEG4 codec to playback. The famouse MPEG4 codec in PC is Divx and Xvid. With MPEG4 codec as key words, you can find many links from the internet.