internett was working fine, then the downloads just fell out and i lost the connection. 4 computer through a hub into a router. only the one i use cannot obtain ip address, ipconfig /renew gives me "Unable to contact DHCP server" Tried to change cable and ports but nomatter the combination of wires and ports everyone else but my cpu is getting internet just fine. frustrating

chk for spyware/malware chk that the nic hasn't failed chk that local firewall is turned off Give a person a fish, they eat for a day. Suggest they internet search and they learn a skill for a lifetime.

Use ipconfig /all on yours and another computer. See what is different. Your system may have an APIPA number or not, depends on your settings. Then consider other tests. Use event viewer for clues. Use a loopback cable to check nic. Use ping to known working system. See also your hosts file. The issue of all of a sudden could mean as above. I am not a fan of the ever turning off a firewall. Firewalls can protect your system from spy/malware and other issues. If a software issue you might consider a restore point.

Are you 100% positive that at one point in time ALL 4 machines successfully had access to the internet at the same time? I only ask this because perhaps your DHCP Scope is limited to allocating only (3) addresses.

Your hub may have failed or the plug got kicked out of the wall somehow (dumber things have happened). Ping the router to see if you can get through to it. Check all cables to make sure these are firmly connected. Connect one client directly to the router and see if you can get an IP assignment now. Could be the hub, could be the cable between the hub and the router if this works.