I have extra P4 PC (Dell Dimension 2400). And I would like to use this PC as NAS. Any advise? What is the best way to make NAS from a PC.
You need to deck it out with hard drives. If possible, try to suit the computer to use eSATA hard drives or SCSI hard drives and set them up in a RAID array to add a level of security and redundancy to your information. Which level of RAID you choose depends on what type of redundancy and error checking you want.
Then you need the software. FreeNAS is an excellent option. Depending on how much RAM the box has, you might want to set it up as an Internet-enabled NAS. This could give you access to your music, pictures, and documents across any network connection. Think about it more like a personal cloud server, and less as just a NAS.