The FDisk utility is no longer supplied with recent Windows operating systems.
To reset disk partition information - boot using the install CD
and choose the install/repair option.
Alternatively there are many third party formatting utils such as GDISK that will do the same thing.
For more advice and other links look at FDISK.com
MSINFO - Windows Diagnostics
FORMAT - Format a disk
FSUTIL - File and Volume utilities
Equivalent bash command (Linux): fdisk - Partition table manipulator for Linux