Wallet versus client machine Can I store my wallet on one machine while running the client on another?
I'd like to help the p2p aspect of the network by leaving a dedicated machine connected...
Here's how I understand your question: You have a spare computer that you'd like to run bitcoin on to help the network. You have a second computer that is your main personal computer; it's also where you'd like to keep your bitcoins. Two copies of the blockchain would waste bandwidth and disk space.

There is a way to keep the blockchain on one computer but to keep your coins on another - you can run the electrum client, and the normal bitcoin client on the other computer. Optionally, you can run the electrum server on your always-up computer, although this requires some command-line knowledge.

https://github.com/spesmilo/electrum-server/blob/master/HOWTO.md