If you want a fixed IP address, a more obvious solution is to not
use DHCP. But then you have to set the IP address, netmask, DNS servers... manually. I did this during install but you should be able to set it later using the proper network administration tool. Make sure not to use an address that falls within the range that your router allocates for DCHP. I presume this is also possible to set in Windows, but I wouldn't know how.