Formatting only deletes the file allocation table or master file table. That's correct. No files are deleted. But they do not appear on your disk anymore and the clusters where your data is saved are available for new data, this means they will be overwritten when copying new data to the "free" space.
You need to format after deleting a partition. its also recommended to format before installing a new OS to the disk. Clean install.
TheMajorMMX - Intel P200 MMX @ 225Mhz - V-Tech (PcPartner) Baby-AT mb w/ Intel Triton TX chipset - Nvidia Riva TNT2 M64 w/ 16MB - 256MB M-Tec SDRAM - Still running.....