What default allocation size should be used with 160 GB internal Hard drive?

[Faster-than-light]

What "default allocation size" should be used with a laptop 160 GB internal Hard drive? The laptop came with the 160 GB size Hard Drive. The re-format is the start of a reload of the operating system on a Dell Inspiron laptop computer.

 

[spooky2th]

4KB

Just let windows do it and set it at default.