I heard of a tutorial that explains how to double the capacity of some brands of harddisks is this true? where can I find this tutorials?

as far as i know its windows "compresion agent" but i think if your file system is FAT32 or NTFS your stuck with what you got.
I may be wrong though.

I heard something about this a while back. I don't rember any of the specifics, but I can tell you I would not trust my data on it (if it worked). Hard dirves are cheap, and getting cheaper; bite the bullet on this one - get a new hard drive.

FAT 32 may be converted to NTFS without dataloss. But once you're there, you can't go back, not that you'd want to.

I think you are asking about Drivespace, which was a way to compress a FAT drive in order to get about twice the space(doublespacing) but this is not possible with FAT32 or NTFS.

I read somewhere else of a guy that was selling a tutorial to double the harddisk space he's explanation was that some fabricants put more clusters than the indicated in the label with the porpose of have something like backups clusters in case that your hdd brake some ckusters the guy says that is there a way to unlock those clusters and double the space. I don't know if that is posible at all

I would like to see this tutorial, as I think someone is pulling your proverbial leg.

Come on lads, the first of April has passed.

LOL.

This is what is commonly called a SCAM. When someone lies to you for money. Do you honestly think a drive manufactorer would market a hard drive at half it's potential capacity? Would a 300GB hard disk have room for 300 more GB's?

"A fool and his money are soon parted" - proverb

If you need more room on your HD, uninstall all programs you don't use. Those that you use seldomly, "pack" the program's directory in a WinRAR file and delete that directory. When you need that program again, un-RAR the program.
You'd be surprised how much space you could save.

But, as said before, HDs are so cheap that you should buy a 160GB disk or something like that.