ethernet

what modem? a cable modem? a DSL modem?

i did install the software for the DSL then i was told that i had to reinstall my drivers and utilities to my computer.

Talk to your ISP's tech support. Isn't there some software that you had to install on your PC to hep with troubleshooting? I know there was with my Verizon DSL.

DSL MODEM

When looking for help/advice, you need to provide as much information as possible.

Simply saying...

my ethernet does not work after intalling new modem

... doesn't tell us anything useful at all.

For starters - what model system/laptop do you have, and what OS/version are you using - i.e. Vista Home Premium 32bit?

i was told that i had to reinstall my drivers and utilities to my computer.

And have you? 

It sounds like you at least need to reinstall the network drivers - which you can get from your system/laptop's 'Drivers & Downloads' page.

You shouldn't have had to reinstall your network card drivers.

Try running ipconfig /all  in a MS-DOS box prompt to see what what it says.

http://www.ncsu.edu/resnet/windows/ipconfig/