Here's my configuration:
1 PC (win 7) cabled directly into a DSL modem.
I want to make my IP static.
I've set the IP with properties on Local network connection; IPv4 ~ but when I validate the connection the Windows Network diagnostics t-shooter wants me to enable DHCP, which undoes my static settings.
No router involved.
Attached are screen shots of properties before & after I change settings.