yep, you can reformat the standard disk to increase the capacity but then this disc will only play on HI MD devices.
If you want your discs to play on net md and mdlp units you can use a regular disc, just be sure not to format the disc in SonicStage before you transfer tracks to it.
I personally do not reformat discs as I have spent years putting a minidisc device in important places - car bedroom etc and I do not want to start again (yet).