ipconfig unable to contact DHCP server

I am connected to a college lan.I get no internet or intranet connectivity on my laptop here though it works fine in other people's pcs and laptops.
Whenever i try to renew my ip address it shows an error 'ipconfig unable to contact DHCP server. Request is timed out'.normaly the net icon shows "Unidentified Network"and Limited Connectivity.
Help please!!

First check to make sure you can get onto the Internet from a friend's house
or another LAN. This will determine whether the problem is on your computer
or not. If you can connect to the Internet elsewhere, contact your college
IT Dept. Many schools have special procedures and track each computer on
their LAN. They may have assigned the same IP address to another computer
or they may need to register your computer with their service.

Of course, you should answer The First Question Of Troubleshooting: If the
problem is new, what changed between the time things worked and the time
they didn't?

If you can't get onto the Internet elsewhere, what antivirus/firewall do you
have installed? Is the computer virus/malware-free?

I do get internet in the main computer center but not in my room or in any of my friends' rooms in my hostel.I contacted my college it dept.They say its a vista related problem.Also i tried to reset winsock using netsh winsock reset, but then on renewing it shows an error about an unidentified adapter or socket (cant remember the exact error, will post it soon) and sometimes shows the original error. Will check for malware and viruses.Thanks

Since you can get on in the computer center, you know your laptop is
working. You forgot to tell me what antivirus/security programs you have
installed and you forgot to answer The First Question of Troubleshooting. I
didn't ask you those things for no reason. For example, there have been
issues with Zone Alarm and AVG 8 updates that impact connectivity. Or you
may have installed a driver for your wireless adapter from Windows Update,
which is usually not a good idea. More information from you will help
narrow down the troubleshooting. If you don't want to bother doing this in
the newsgroup (and that's perfectly OK - I have a son in college and I know
how intense things get for you guys), then apply the same deductive
reasoning to your own troubleshooting efforts.

I'm not sure if adding anything caused the problem. You see i bought the laptop just a little while ago and never tried to connect to a lan or wireless network before i came here. I did use a dial up but have not been able to see if that has been affected or not. I also tried to connect to our wireless network but got the same dhcp error while renewing. I was using quick heal pro. I even used the "Restore C:" option yesterday but to on avail, I still get the same error. I am currently using avast till i can reinstall quick heal as my original cd is at home. Is there any i could reinstall vista on the laptop? I an not sure if restore c: did that or not. And my laptop is malware and virus free. I really have no idea what to do now.

You're better off sticking with Avast. When you say you can get on at the
Computer Center, is that by wireless or by wired (ethernet)? If you can get
on by wired, then you need to see if the wireless works anywhere else. Does
the wireless manager (Windows or the adapter's software) at least see the
wireless networks?

If the wireless sees the wireless networks but you can't connect, you may
have the wrong encryption level/passphrase. Or the router being used is old
and isn't compatible with Vista. Check with your school's IT Dept. to see
if any other computers running Vista can join the network.

I have no idea what "Restore C:" means. Your laptop mftr. will have a way of
returning the computer to factory condition. Refer to the laptop manual,
the OEM Help files on the computer, or the laptop mftr.'s tech support site
for how to do this. I have no idea whether returning the laptop to factory
condition will be useful because I don't know the answers to my questions
in the first paragraph.

There is really no way for me to continue troubleshooting this machine
without being able to see it. I'm sorry, but you would be best off taking
the machine to an IT person or a computer repair shop. It needs to be
tested outside of your own network.

I restored vista to its factory settings and the net finally started working.