Turning a modern games console into a NAS

Is it possible to turn a Wii, PS3(Slim250GB) or Xbox360(Slim250GB) into a NAS. I presume if you can install FreeBSD on them then FreeNAS should work? If possible I would also like to use the disk drive over the network and plug my 2TB external USB drive in.

I have these consoles around but no intent to use them and it isn't possible for me to sell them right now, since they normally use quite small amounts of power even by todays standards(Especially the Wii), it feels like they would suit the role.

No point, Buy something like a Rasberry Pi, install Linux, Buy a USB Hub, install Hub into Pi, Install USB HDD into Hub. Done. Want something better? Go build yourself a proper NAS. A console will do a worse job than a rasberry Pi in terms or functionability, cost and power to run. A Pi is $30, a USB Hub is $10, you already have a 2TB HDD, honestly $40 for a budget NAS server is nothing to turn your back to.

FreeNAS is really for a server with redundant hard drives with lots of ECC ram. It uses a file system called ZFS made to protect data. If you just want to put a hard drive on a network to share it out anon is right. I don't recommend buying a NAS box though because they don't have ECC ram. You can buy a cheap entry level server motherboard, a 64 bit processor and 16gb off ECC ram for way cheaper than a crappy retail NAS box anyway. Then freenas runs off a USB flash drive. Put in two WD 3TB red drives and bam, kick ass raid that will protect your data. At that point you can run all of the other fancy features that freenas offers.

If you knew how to bypass all the Hardware gubbins yes, yes you could. But that is also a problem: you need to pass all the hardware gubbins which takes a lot tinkering around. I agree with WendellWilson: "You can buy a cheap entry level server motherboard, a 64 bit processor and 16gb off ECC ram for way cheaper than a crappy retail NAS box anyway. Then freenas runs off a USB flash drive. Put in two WD 3TB red drives and bam, kick ass raid that will protect your data. At that point you can run all of the other fancy features that freenas offers."

What i'd suggest is getting a cubieboard and putting openmediabox on it. (you will likely hit a transfer cap if you plan to utilize more than 2 or 3 drives at a time though.)

The cubieboard has a single SATA port which can be plugged into a port multiplier to get up to 5 drives.
What's even more convenient is that you can probably put the whole thing in the 5.25 bay and have it Acess HDDs in your box and run a dedicated NAS server from within your desktop box. ( provided it's not mITX )