Home network fixed...finally

It's been a week since my sister complained about her PC not being able to go online. It's just strange. I know my wireless router is too far away from her PC, so I purchased a wireless AP and put it upstairs. It worked for a week or so. When I check her computer's wireless connection I can see that it's actually connected to the wireless AP but its IP address is not in the same range with my home network. I couldn't figure out why. Perhaps I should set the wireless AP as a bridge? Anyway, I was gonna run an extra long cable from the router to her room and take out my $99.95 wireless AP. Then I got an idea. Why not move the router upstairs? In less than 30 minutes her PC and get on again! I hope this is the end of the story. :(