WiFi- connection Limited/Not connected

Hello,
I am using ASUS laptop Model: X401U-BE20602Z SKU: 8850089[14" Laptop - 4GB Memory - 500GB Hard Drive] with windows 8.1, 64 bit. bought a year back.
The internet connection was very good with normal speed. Few days back when I installing a software, as advised therein I put off the net connection in my pc and then installed that. Subsequently when I started/put on the internet WiFi, the connection is not working. Even if it is connected there shows only "Limited" and the internet is not working at all. I tried all the trouble shooting methods as per the help page from ASUS and from the internet and got the following results were appearing. And I am struggling for the last five days in vain.

The trouble shooting results are as follows:
1)This computer is set to manually connect to BigPond (Broad Band WIFi)
2)A net work cable is not properly plugged in or may be broken
3)Problem with wireless adopter or access point
The latest narrowed down results are:
4)Security or firewall settings might be blocking the connection-(Filter name: NatAle Port Filter)
5)The default gateway is not available.

I did all the procedures relating to the above 5 trouble shoot results. No use.

If the Ethernet cable is connected with the modem the internet is working well and also if we operate close to/near the modem without the Ethernet wire/cord the WiFi is working.
But the WiFi is not working as in the past, if I work in my bedroom - 45 feet away from the modem. Other 3 laptops and few tablets, being used by my family members are working well with the WiFi, except mine.

I am become mad, so to say and completely upset over this problem.

Kindly advise me or guide me how to fix this problem. Please reply:- sbidsel@yahoo.com
Expecting your favorable result oriented guide lines at your earliest.
Thanking you in anticipation.

With Regards
SelDei
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