320GB HD = 320,000,000,000 bytes
The SI standard 10^9 = 1,000,000,000 bytes
Since its in binary, you'll see 1GB as 8^10 = 1073741824 bytes in Windows
320,000,000,000 bytes / 1073741824 bytes = 298GB
HD companies use the SI standard, so why are they getting sued?