Beware of fake Sony 500G Micro Vault

I visited a computer mall in Shanghai. A computer dealer offered me a 500G memory stick at a price of about $US 50. I thought it was impossible, but the dealer stuck his stick in the computer and it showed "493 GB free". I assumed I made the deal of my life. When I came home, it was the same but also showed "FAT32" so I immediately understood my money went in vane. In practice, every file I saved into the drive shrunk in size and only the name was left. I am also concern regarding Trojan takeover, but I keep an up-to-date Internet Security Software.

Conclusions:
1. Don't buy anything you did not intend to buy.
2. Don't leave the city before you checked your items in real life, not at the store.
3. Keep your credit card vouchers in a safe place.