Several things you can do.
- Setup a server Windows/Linux with a couple of big HDs in it and share them out.
- Windows Home server, fairly well rated but you have to buy it bundled with the hardware. Some nice features like auto backup / restore.
- NAS Server, I'm not a fan but they work well.
- Add an external HD to a machine and share it out, go eSATA if you can.
Make sure you backup your data, I still recommend a couple of external HDs, rotate through them. Keeping one off site or at least in a fireproof safe.