Wireless low / very low signal strength

[Willeh]

Hey, My wireless signal has always been from low / very low, sometimes rarely it goes to good.
I've found both the usb network wireless adapter and the wireless router [both from belkin]. I've also prepared a diagram to show the position of both components.

PC A, is directly connected to the internet with a Belkin ADSL Modem High speed wireless g-router. Search this up on dealtime.co.uk for product specs, I can't seem to paste the link:

f5d7633-4 uk ADSL router Belkin

PC B, is connected to the internet through the router with a Belkin Wireless G USB network adapter. Link for product specs:
http://uk.shopping.com/xPF-Belkin_Belkin_F5D7050


Both pcs are located upstairs, as you can see in the diagram below [I hope it's easy to follow]
http://img.photobucket.com/albums/v1...ssNwDigram.png

It's not really that far away from room pc a to b, it's about 15 normal steps.

Anyway, All I need now is tips in which to increase signal strength, I'm planning on wireless networking on pc B so signal has to be strong and such

Thanks

[Osiris]

you can always get some range extenders