What OS are you using? I assume you are using some version of Windows. If so, install the latest ATI CCC version for your OS and then be sure to designate your primary display and then extend it to the secondary display. Both displays are working, you just need to configure CCC/the drivers.
Regarding the KVM question,this link at Newegg shows they have 7 KVMs capable of supporting 4 computers and 2 monitors. Scan the reviews and take your pick. Expect to pay at least $200US.http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100006792%20600012892%20600029612&IsNodeId=1&name=2%20Ports