!HELP! Wireless !HeLp!

Hey all, well i have D-link wireless internet I have a [D-link AirPlusXtremeG High speed 802.11g wireless router a DI-624] for a router and for reciveing i have a [AirPlusG 802.11g/2.4Ghz Wireless USB Adapter, a DWL-G120]. Well my singals have to go upstairs then through 3 walls and so it sux alot. My signal strength is always at like 15, and it is so slow, when i play diablo(a online multiplayer) i LAG soo much and loose connection alot, but sometimes internet is fine. My dad said that he wont let me run a E-net wire all the way to my room outside or inside the house not on the edges or anything, but he said that we can extend the reciver to eliminate 1 wall, hoping that will make a big difference, which it might, so we would have to go get a USB boster wire right, i was wondering if theres anytihng else i can do? Please please help, THX in advance!

 

http://www.dlink.com/products/?pid=267

 

wireless G is 54Mb so 15 is basically 15Mb. That's what shows up on mine when I get down that low. But that is still plenty fast considering cable is 10Mbs.

That is unless D-Link measures theirs differently.. so yeah.. give us more info.