First off, I get the feeling that your dad has the router in his room for a reason ... like not allowing internet in your room. I'm not advocating configuring another router to sneak internet access into your room. If this is what you're doing ... then ignore the following:
Essentially what you want to do is bridge the 2 wireless routers. Configure your router with the same SSID and WEP that your dad's router has.
Here's what I would try: Router 1 (dad's) Router 2 (yours) I dont know your IP address range, but lets say it's 192.168.1.x
Router 1 IP address 192.168.1.1 Subnet Mask 255.255.255.0 Default Gateway x.x.x.x (public - ISP)
Router 2 IP address 192.168.1.2 Subnet Mask 255.255.255.0 Default Gateway 192.168.1.1
Turn off DHCP on Router 2 ... Router 1 will do this for you. Leave NAT running on Router 2 so Router 1 will route to your pc.
This should work for you ... good luck.