How can I get ethernet or fast internet into my room upstairs?

I have a modem from comcast downstairs on the first floor. I bought a wireless card for my PC in my room upstairs, but the connection is very slow and spotty. I cannot run wires from my basement to the second floor because our house setup is weird. Is there any such thing that I can plug into a power outlet with ethernet out of one end and plug it into my PC to get a faster connection? What else can I do other than a wireless card or drilling a whole in my ceiling/floor?