Go to the "Start" menu in Windows. Navigate to "My Computer," right-click on it and select "Manage" from the drop-down menu. This brings up the "Computer Management" window. Select "Disk Management" located under the "Storage" category. This brings up a list of drives, including your flash drive, on the right side of the window. Select your flash drive then right-click to show its drop-down menu. Choose the "Delete Partition" option. This creates the entire flash drive as one portion of unallocated space. Right-click the flash drive again and then select the "New Partition" option. Follow through the "Partition Wizard" dialogue by selecting the partition type you want to create: primary, extended or logical drive. What partition type you choose depends on what function you want your flash drive to serve. Continue through the "Partition Wizard" dialogues by choosing the partition size. You can also assign a drive letter to the flash drive; otherwise the program does it automatically. Additionally, you can type in its "Volume Label," change its format speed or convert it to an NTFS volume. Click on "Finish" to complete the process.