I'm wondering how can I hide a partition from a pc and still be able to run software installed into that partition, I followed the steps of this question's first answer but I can't access any data from the hidden partition.
If all you want to do is hide the drive letter, you could mount the partition under a path. For example, if you don't want your temp files to fragment you system drive, you can make a "temp" partition and mount it under C:\temp. Then everything written to C:\temp will actually be written to the other partition.
Unless you know where the partition is mounted you (through windows) wouldn't easily be able to find it unless you know about these things.
I wouldn't really call this hidden.
For a real hidden partition you could make an encrypted volume with TrueCrypt and then make a hidden volume within that. http://www.truecrypt.org/docs/hidden-volume