Rangemax Wnr834b

hi have a rangemax WNR834B wireless cable router.
its a netgear make and for some reason i do not get good signal strength throughout my house, its supposed to have a good specification as you can see for yourself in the following link:

http://www.netgear.co.uk/rangemaxnex...rs_wnr834b.php

but on my laptops, psp etc i do not get good signal strength in most rooms in my house, and the internet cannot connect as the signal strength is too poor?
can anyone help me in fixing this problem or is it a problem that cannot be fixed. maybe i have to change some settings or something on my router?? or it might be the fact that my walls in my house are too thick so the signal is greatly lowered?
any suggestions may help. thanks