I have an Acer 4730z laptop which has Ralink 802.11n wireless LAN Card and has Windows vista home premium.

I bought this laptop in US and there I used with D-link DI-524 router and had no problems... I also used it while traveling within US at hotels, airports etc and had no problem with wireless connection.

Now the laptop is with my father in India. There he has Pronet PN-108WRT - 108Mbps Wireless Router. Detail specs of this router are here.

Now the connection works fine if he is very near to router. But if he goes to next room it stops working. After some setting changes, he was able to make it work for about a min but then again it disconnected.
After that when he checks available wireless connections, it just shows pronet for few seconds and then it doesn't show.

Of course, first guess can be that wireless chip/signal is not strong but I will be really surprised that it can not penetrate even a single wall.

Now, he also has sony laptop (with Intel(R) Wireless Wi Fi Link 4965 AGN) and that is working perfectly.

My guess is that may be the acer is trying to connect at 802.11n network while router works only on 802.11b/g network. Could that be a problem?

He did update drivers for the Ralink but still did not make any difference.

What other things we can try?

Configure adapter and router to not auto-sense data mode and rate. Configure each device to use G at a specific rate. Specifying a particular channel may also help. Are there any cordless phones or other wireless devices in the area using the 2.4 GHz. Band? 2.4 GHz. Cordless phones, in particular, are an anathema to WiFi.

Thanks for your reply.
The cordless phone works in home works on 5.8 Ghz and there are no other wifi connections in the area.
In acer laptop, I could not find any place where I can set it to use G. Do you know where one can set it.

My father tried to change channels but that had no effect.

No, I'm not familiar with ProNet or Ralink. ProNet doesn't appear to have product manuals on their web site and Ralink looks like they only provide wireless chipsets for inclusion in other products. The documentation that came with both products should indicate how to configure the wireless settings. Configuring at minimum the router to use G mode instead of Super-G should suffice.

Also, if the laptop has it's own wireless controller (button on left hand side of keyboard), try turning it off.