Is there a specific way to block these addresses then?
In Win XP, there is no obvious and easy way. Windows built-in firewall doesn't allow this sort of IP address filtering - nor does OneCare (say that over and over, you end up saying wa*ker!).
I digress.
Some other software firewalls may allow you to block a source / destination address or address range. I don't know.
Hardware firewalls may allow you to do it - my Netgear firewall doesn't allow IP address ranges (just domain names) to be blocked, but I simply set up a static route, so that the route to 85.255.112.0/20 (the /20 means a 20-bit subnet mask, i.e. 255.255.240.0) is directed by the firewall BACK to my own computer. Similarly for 69.50.160.0/19.
Crude, but effective!
SD