first of all, set the MTU back to 1492...
for static ips, assuming you are running windows xp, open the network connections folder, right click on the connection you are using for your network (most likely Local Area Connection), click properties. In the "This connection uses the following items:" box, select Internet Protocol (TCP/IP) and click the properties button. Change the top radio button to Use the following ip address, enter an ip address (i would suggest 192.168.0.200 and go up 1 for each other computer, ex. 192.168.0.201) subnet mask should fill in automatically when you select it, if not, enter 255.255.255.0. your gateway will most likely be 192.168.0.1. you will also have to enter DNS servers, so click start-run-cmd, type ipconfig /all and make a note of the DNS servers. if there is more than one, put one in the preferred DNS server box and one in the alternate DNS server box. ok your way out of everything, and reboot.