Interesting slow booting problem found on a network. This is a good check for whenever you have a slow starting PC.
I noticed on a 10 PC network that one PC was particularly slow to boot. I checked the ethernet wiring from the PC to the switch with a cable tester and it all looked OK.
I then decided to check the ethernet card, thinking it might be damaged. I checked the TCP/IP properties and noticed that it had DNS server values of 18.104.22.168 and 22.214.171.124. Very unusual since this network was supposed to obtain the DNS server addresses automatically.
I did a quick Google search on the servers IPs and it looks like they are related to some Trojan. After removing the hard coded DNS server addresses the system boots up quickly now.