I have a dell inspiron laptop. The OS is Windows Vista.
My lappy is working fine in my office n everywhere else but in my apartment it is very difficult to connect. Showing Firfox is not able to connect to the server. I have to try several time it to be connected. And the connection is losing in between also. I could not speak through Skype due to this problem. There is no problem for my connection because other computer is working fine. The internet providers also came and check. They said the problem is with my computer.
I checked IP has DHCP enabled and the default gateway is empty. I could not able to remove DHCP enabled.
I also tried command line window
ftp localhost (enter)
It shows
Connection refused.
Please help me to fix this problem. My internet is working in office but not in my Apartment

The problem may be in your wireless router setup. You may need to select a different channel. If there are other nearby wireless access points (common in Apartments) then they may be "stepping over each other".

Thank you very much. But I am using a LAN connection not wireless.
Still it is not working properly. I disabled Mcafee and all firewall

Switch your network connections to test the same computer on the other network cable that is known to be working.

McAfee is unlikely to be your problem unless you are using the personal firewall. Do not use more than one virus scanner or firewall program at a time. Your Windows Firewall is also not likely to be a problem. It is typically ON or OFF as far as connections go.

With wired connections, if you are getting a "limited or no connectivity" message, it is likely your network cabling.

Bad cable or bad port. I suspect a bad cable.
Do pings with a large packet length like 8192 to your router. If you get errors that's a good sign of a bad cable.

The internet providers did pings there was loss of packets 11% with my computer but when they did it with their computer there was no loss. They said the cable and connection is good the problem is with the computer

You have to fix the packet loss. In order for their test to be valid, they would have had to use your cable.

It could be a network setting on your computer or it could be a bad network card or motherboard controller. You have to fix the packet loss.

The cmd you need to issue from the CMD prompt is ping 10.0.1.1 -t -l 8192 where 10.0.1.1 is the address of your router which is probably 192.168.1.1. The "l" is a lower case "L"