I already googled this issue and realized that it is very individual problem.
I don't need network support on this old laptop (for now) and I want to disable it completely.
I made .bak copy of /etc/network.conf.
Then I edited /etc/network.conf and changed
DHCP="no"
Well, it didn't speed up booting actually.
What else can I do to disable network configuering on boot and to boot faster?