My laptop won't connect to the internet anymore...?

I know this is a common question, but it was able to connect not long ago without hassle. Now it will not connect at all. I've tried:

Flushing the DNS, defragging,scndsk,chkdsk,cleaning temp folder, virus scan,Ccleaner,scan in safe mode, restarting computer,restarting router, turning off firewall, and what seems to be everything I could do...Can anyone help me figure out what the problem could be? My other laptop, as well as the desktop acting as a client/server work just fine.

The laptop is a Dell Latitude D600
Windows XP Home edition
SP2

Thank you

I realize most of these things would have no effect on a LAN connection, or any type for the matter, but it's the suggestions that most people usually give me for these type of questions, so I figured I might as well move them out of the way.

In relation to my hardrive being damaged or anything wrong with the router, like I said, not only do i have 2 other laptops working perfectly with it, but also a desktop acting as a server/client that works just fine.

I have checked and it is the ip address...I can't believe I missed that of all things -.-;; Expect to get your points person who noted the ip address =P

What firewall you using?
And can any other programs access the net like a messenger or anything?

run an IPCONFIG /ALL in a command prompt and see if you getting a proper addreess...
if it starts witha 169 then you may have ome ip address issues..

network card went out?

Try re-install NIC driver (network card driver).

All the things that you tried would not have solved any problem, to be honest. Im assuming that the driver for ur wireless adapter is still installed, you can check in device manager.
I know this seems far fetched, but it is possible that ur motherboard or wireless adapter is damaged. Dell doesnt exactly build their laptops with the best qualtiy components. If ur laptop is still under warranty then you can arrange for it to be fixed free of charge.