Does Windows recognise the disk as a 800mb disk or a 702mb disk (in My Computer > Right click on disk > Properties)?
If it recognises it as a 702mb disk it may be that your CD-RW drive needs an update of firmware, you'll probably find it somewhere here
http://forum.rpc1.org/dl_all.php, but make sure you get the right one! I can't stress that enough!
If Windows recognises it as an 800mb disk ignore the firmware issue...