I can't use all space of my pen drive?

It seems that it devloped some bad bits.

Plug it in.
Open the explorer and right-click your drive. Sellect "Properties".
Sellect the "Tools" tab.
Click the first button: "Check now..."
Check the 2 boxes and click "Start".
This will scan the unit for any error. If it finds some bad sectors, it will flag them as bad and you will no longer attempt to use those.
It will effectively "jump" over the bad areas and allows you to use the rest of the space.

You must treat it as Unreliable from now on.

Electro
May 2011