Why won't my computer connect to my Linux access point?

I'm setting up a Raspberry Pi as a proxy access point which accesses the internet via my USB tethered smartphone and is connected to my Windows PC via Ethernet. The internet works fine on the Pi, but I can't get my computer to connect to the Pi as it should. This is my computer's ipconfig when wired up to the Pi:

Ethernet adapter Local Area Connection 4:

   Connection-specific DNS Suffix  . : 
   Link-local IPv6 Address . . . . . : fe80::1d6b:1514:ccb5:28cc%23
   IPv4 Address. . . . . . . . . . . : 169.254.123.199
   Subnet Mask . . . . . . . . . . . : 255.255.0.0
   Default Gateway . . . . . . . . . : 

Ethernet adapter Ethernet:

   Connection-specific DNS Suffix  . : 
   Link-local IPv6 Address . . . . . : fe80::c0e:bb47:359a:cf33%13
   Autoconfiguration IPv4 Address. . : 169.254.207.51
   Subnet Mask . . . . . . . . . . . : 255.255.0.0
   Default Gateway . . . . . . . . . : 

And here is my /etc/network/interfaces file on the Pi.

auto lo

iface lo inet loopback

allow-hotplug usb0
iface usb0 inet dhcp

iface eth0 inet static
address 192.168.20.1
network 192.168.20.0
netmask 255.255.255.0
broadcast 192.168.20.255
gateway 192.168.20.1

I've also tried it with this configuration, with the same results:

iface eth0 inet static
address 192.168.42.200
network 192.168.42.0
netmask 255.255.255.0
broadcast 192.168.42.255
gateway 192.168.42.129

192.168.42.129 is the gateway that my smartphone uses, for reference.

Any help would be greatly appreciated.