Well I would look in the disk manager in the control panel and see what the partitioning on it is. it may be partitioned wrong. You can delete and repartition it to the full 4 gig. then reformat it again.
My Computer
At a glance
Windows 7 x64 Ultimatei7 96012 Gig Corsair DominatorNvidia 480
Computer Manufacturer/Model Number
Scratch built
OS
Windows 7 x64 Ultimate
CPU
i7 960
Motherboard
Asus P6X58D
Memory
12 Gig Corsair Dominator
Graphics Card(s)
Nvidia 480
Sound Card
Maudio Delta 44 + breakout box
Monitor(s) Displays
Dell UltraSharp U2410 24in and Samsung 21 dual monitors
Some questions:
Do you mean 256mb? (I am assuming you are)(1000mb=1gb)
Is this a new flash drive?
where did you get the drive?
Was it working previously with a different OS?
My Computer
At a glance
Win7 Home Premium 64xIntel Core 2 Duo P7450 / 2.13 GHz (2.29 with ...4 GB PC-6400 Hyundai (2X2) at 800MhzNVIDIA GeForce GTX 260M 1GB DDR3 VRAM
Computer type
Laptop
Computer Manufacturer/Model Number
ASUS G60-RBBX05
OS
Win7 Home Premium 64x
CPU
Intel Core 2 Duo P7450 / 2.13 GHz (2.29 with Extreme Turbo)
Memory
4 GB PC-6400 Hyundai (2X2) at 800Mhz
Graphics Card(s)
NVIDIA GeForce GTX 260M 1GB DDR3 VRAM
Monitor(s) Displays
16" LED Backlit
Screen Resolution
1366 x 768 on laptop 1600x1050 max res on 22" external mon