Why does my wifi keep disconnecting if I move more than 10 metres from the router?

I have a netgear n150 and it is generally quite good but it was a cheap route rand the internet can get slow and drop out up three times daily. The previous router was a netgear dg834b which was extremely reliable and never had any problems with until i made a mistake and screwed it up. I have an acer aspire D255 netbook whih works well with it until i go beyond the 10 metres, and i also have a windows 7 HP desktop which was very reliable with the old router but it tends to get slow and disconnect frequently. My desktop uses a netgear adapter which came with the old router. what can i do? thanks