http://freenetproject.org/home.htmlShare, Chat, Browse. Anonymously. On the Free Network.
Freenet is free software which lets you anonymously share files, browse and publish "freesites" (web sites accessible only through Freenet) and chat on forums, without fear of censorship. Freenet is decentralised to make it less vulnerable to attack, and if used in "darknet" mode, where users only connect to their friends, is very difficult to detect.
and from http://freenetproject.org/download.html
Generally a 1GHz processor and 1GB of RAM should be fine. Freenet will run on smaller systems, but it uses at least 128MB of RAM, so unless the system does nothing else it will struggle in less than 512MB. However, the processor is less of a problem, people have been known to run it on 400MHz Pentium 2's or ATOM's, although downloads and browsing would be slow.
Freenet will use a portion of your disk for storing data, you can configure this to any size from 100MB upwards, but we recommend at least 1GB. Freenet also uses disk space for your downloads. Freenet's memory usage is approximately 192MB plus 1MB for every 2GB of datastore.
On 64-bit Windows, we will install a 32-bit Java Virtual Machine because of limitations of the Java Service Wrapper. This will not necessarily auto-update itself, so you may need to update it occasionally.