I'm looking at setting up a media server at home but I have no idea what sort of specs are needed.
Can I just pick up an old PC and stick some extra HDDs in it? There are a few cheap PCs for sale that I have seen with Core 2 duo CPUs and 1-2 Gb of ram, will these work for a media server, or will I need something better like an i3 or i5 etc?
The goal is to stream content to the TV and 1-2 laptops (not necessarily all at once), as well as having a place to store photos and other files so they can be accessed by anyone on the network.
A basic home media server doesn't have to have a whole lot of power necessarily, especially if you aren't reading and writing data to multiple destinations simultaneously. I would recommend a 2 Ghz dual-core processor minimum still to give you responsiveness, but your big factor is going to be storage space and the level of protection you need. For example, do you need 1 TB of storage for all of your data, or 4 TB or more? If you are wanting to protect your data a little more, then you can consider setting up a RAID array, though most of your pre-built cheap systems do not support RAID and even if they do, their onboard basic RAID controller is more likely to fail than anything and I wouldn't recommend even trying it. However, if you really want to duplicate your data, then set up a RAID 1 of two identical drives, and find something high-performance and high quality to fit your needs. WD Red hard drives are known for good performance in NAS devices, though personally I would go with WD Black for the longevity and these are truly great performance hard drives. Just be aware that RAID is NOT a backup system. It's meant to offer continual up time in the event that a single hard drive fails. You still should be backing up your data to a separate location, such as an external hard drive, on a regular basis.
If you don't need to go with RAID, then you should be able to use most any pre-built desktop system so long as it still supports enough storage space for your needs. If you need 4 TB of storage space, but your older computer only recognizes a maximum of 2 TB hard drives, you would need two drives in the system obviously, which means the computer needs to support two SATA connections, two drive bays, etc. Windows 7 or Windows 8 can work just fine for dishing out files to a workgroup, but there are other alternatives like linux distributions specifically designed as media content servers, but personally I just don't know them so I can't help you with recommendations on that.
If you don't want to hassle with a whole computer system, you can look into a nice quality NAS device. I recommend Synology brand, they have great quality. The nice things about these is they are easily expandable (many models ranging from 2 bay to 5 bay or more) use very little power, and are easy to manage. The down side is they don't use standard desktop hardware, so if you needed to replace out a failed power supply or CPU fan you're not going to just be able to use anything.