Just for the record, your PC can be fooled into thinking a USB stick is larger than it is, so simply plugging it in and seeing what capacity it says it is, is not necessarily the truth. I don't know how they do it, but these fake USB sticks trick your PC, so a 4 GB stick for example, might show up as 32 GB on your PC.
I've tried that programme in OG's link (H2testw) quite a while ago and this is probably one of the few ways to safely determine the true capacity of your USB stick.
If I remember correctly though, it does take quite a while, so be prepared to leave it running for a while.