XP CD Writing Wizard reports false value for 'free space' on blank discs

My Internal 'SONY CD-RW CRX100E' drive was freezing and making coasters at the lead-out stage when using Nero6. I deleted the program (uninstall file was corrupt), and have since tried (with a number of blank cds) to burn files just under 700mb with the windows xp cd writing wizard. Each time I get the following message:

Cannot Complete the CD Writing Wizard

This CD does not have enough free space for all
your files. There is 595 MB free space on the disc,
and 699 MB to be written. To continue, please
reduce the total amount to be written by 104 MB.

This is a pain in the ***. I haven't interfered with any hardware since it started playing up so i'm thinking it must be a driver or device settings problem. I'd be grateful of some technical advice.

Thanks,
-rob.