I had the same problem with mine. What you need to do is, useing the USB cord for your modem (I stole mine from the printer
use that to plug your computer into the modem, no router or anything just straight into the modem. This "Should" get you online, use the computer to get to dell and find your drivers. I myself use a wonderfull program, but unfortunally you have to pay a one time fee (29.95$ I think). I payed it like 3 years ago and still have access to the program and use it all the time. www.drivershq.com is where I got it. It will tell you what drivers your missing and even let you get just that driver.
What I did was last time I tried to reinstall everything I got that program first, downloaded all the drivers it told me I needed into a file on the desk top. After the computer was in tip top shape, I burnt those drivers to a CD, and the next 2 times I had to format that HD all I had to do was insert the CD and update all my drivers
I recomend the program for all who want it
FYI I am not, repet NOT an expert on windows or Dell, just had so much dealing with them in the last 4 years I know my way around this exact same problem!! SO take my advice knowing that Thanks