File Sharing From iMac to MacBook?

[Darkroom]

so i've set up my iMac to let the MacBook receive files over my network. however, the finder on my MacBook displays 2 computers found:

1. a PC with the same IP address as my iMac
2. my iMac

i'm using my iMac's AirPort to share the internet connection throughout my apartment (since i don't have a wireless router), but why does the PC show up?

 

[r.j.s]

You have some kind of Windows sharing enabled as well.

 

[markojug]

Someone is using your Mac's connection for their internet. You have to disable something but i don't know what.

 

[Darkroom]

You have some kind of Windows sharing enabled as well.

under Sharing on my iMac, i have selected:

1. Screen Sharing
2. Fire Sharing
3. Printer Sharing
4. Internet Sharing

seems like it's my printer. when i have Printer Sharing selected, i can connect to this server as a guest, but when i deselect the Printer Sharing on my iMac, connection to the "PC" fails.

is there a way to remove this "PC" from the Finder?