ok,
this is sort of bug in XP, when you have 2 optical drives.
Did you also get error "Incorrect Function" when you insert a blank CD/DVD and click on it????
The workaround is, 'right click' on that drive's icon go to "Recording" tab and check "Enable CD recording on this drive". (let the drive be automatically be selected, but you can change it if you wish).
Now this drive will show correct size of the disc inserted
.
(but, at the same time, now(surprisingly!!) your other drive wont
, thats why i call it as a bug
)