Windows Image Writer to make a bootable Chromium OS USB drive (*), my 8 GByte USB flash memory stick has been partitioned to a 2 GByte size.
Go here to recover 8 GByte capacity.
Click Start , type CMD in the search field and press enter key to open the Windows Command window. The default command prompt should be C:\> .
The prompt changes to reflect the actions done within DISKPART command, DISKPART> .
DISKPART> LIST DISK
This command reports the number 0 represents the hard drive, and the number 1 is assigned to the USB drive in a single HDD PC configuration.
DISKPART> SELECT DISK 1
Disk 1 is now the selected disk.
(Replace the number 1 with the variable assigned for your USB drive in the previous command.)
DiskPart succeeded in cleaning the disk.
DISKPART> CREATE PARTITION PRIMARY
DiskPart succeeded in creating the specified partition.
Voilà. Next make format by usual way...
*) How To Turn Your Netbook Into a Chromebook with Chromium OS - http://lifehacker.com/5820358/how-to-turn-your-netbook-into-a-chromebook-with-chromium-os