Wireless adaptor - rubbish

Hello, I am now on my third wireless adaptor (why its taking me three to realise they are uselss is beyond me). My partner uses the computer upstairs in what we call the office. Its an oldish Dell PC and needed a wireless network adaptor to get on the internet. I have bought the usb type one and plugged it in. The first one he had worked ok, but it broke. Since then i have bought two of them and he gets an absolutely terrible signal on both of them. I can take my laptop upstairs and the signal is absolutely fine. No problem at all - so i dont think its a problem with the signal. More to do with the adaptor. Is there anything i can do to sort this out as i am sick of him whinging about it to be honest!!! I have a wireless router hanging about. Is there something i can do with this? Plug it in or something to boost the signal? I was going to try and get a repeater, but i figure that if i am sat in the same place and the signal on my laptop is absolutely fine, it must be the adaptors that are the problem. I dont mind spending a small amount of money sorting it out - but ideally i want someone to tell me i can plug my spare wireless router into it and get a signal from that!!! Can anyone help please?

The location of the USB Wireless Adapter is almost surely the problem. What about installing a PCI Wireless Card with and external antenna that you can move to get the best signal possible, or one that has two external antennas?

pci wireless adapter with external antenna
linksys external antenna wireless adapters

Another possibility is to bridge the two wireless routers together if they support that.

Connecting Two or More Wireless Routers, Wireless Bridging

If the router doesn't support bridging then give DD-WRT a try: