My home network contains 10 computers a router and a switch

I have a 512/128 kbps ADSL connection and i only get low download speeds max. 36 kbps average 5-20 kbps and it may be even lower that now i am always using prozilla to download anything.

as a step to identify the source of the problem i used nmap as follows
and i received the results i was hoping for but i do not know what it was
there were too many ports named as [unknown]
and after googleing for a while i found no clue about what they refer to.

There are two things i am worried about
1. pear-to-pear applications (kazaa, imesh, limewire,... )or torrent clients (bit comet, bit torrent, bit lord, azureus ,...)

2. spyware and the possibility that they would be eating all the bandwidth.

Using the ports i received from the nmap outcome i could not identify any programs.

So what would you do if you were in my place...?
Do you think that there would be other reasons that may slow the overall network performance?

I am waiting for your replies.
Thank you very much.

PS. I am the only one using Linux.

If your router has a firewall, you can block on the router all the ports on the internal network from outgoing except the ones you're interested in (usually HTTP, HTTPS, DNS, DHCP, SMTP, etc). Granted, it might depend upon your router as to how much tweaking you can do.

I have a linux based router that I can actually upload firewall rules to. So I reject all outgoing requests to those services. I drop all incoming requests to those services. That way people on the outside don't know the port is closed, but the people on the inside get a clear rejected message.