|This is a very common situation.|
The issue is that there are two established definitions for what GB means.
The definition used by most drive manufacturers s that 1GB=1,000,000,000 bytes.
Windows uses the other definition where 1GB=2^30=1,073,741,824 bytes.
Divide 160,000,000,000 by 1,073,741,824 and you get about 149GB.
That is the capacity of your drive.
Also see this article: