Is there a secret part of my hard disk?

I'm not quite certain what's going on with your hdd, but do remember that hard drive capacities are base 10, not base 2 like most other capacities on a computer.

What software are you using to erase your disk and what sort of file system are (were, hehe) you using?
All of you manufacturer stated hdd capacity should be available to you.

While a GB of ram is 2^30 bytes, a GB of hdd capacity is 10^9 bytes.

It's possible you have bad sectors or have something strange about your low level formatting if you've messed with it(defining how many tracks, sectors per track ... etc.)

 

Capital B stands for bytes, if I'm not mistaken.
Lowercase b stands for bits.

 

Unreachable implies that there is a BIOS, O/S or Software limitation.
Might depend on how old your stuff is.

There at one time was a manufacture partition that remapped bad sectors with "spare" good ones. It required special software to update. Don't know if this method still exists or if that is what you are finding.

 

No argument on vista (it came with my laptop).
Ok, as an internet appliance, but as an OS...

No idea what you are using to scan your disk.
While I haven't researched it, I do have some indication that Vista keeps some data outside of the defined disk file system structure.
This idea may or may not be correct.

 

Ok, that I kinda know about (not a lot).
There really isn't a file -- it's some sort of alias link.
To get there directly from mycomputer you need
c:\users\xxxx\docments where xxxx is your user id.

All of these funky links have the funny arrow icon on them.

EDIT: or you can just click the xxxx directory and get the same thing.
Or it really is organized the old way but vista forces you to use the overlayed new links