Cannot connect internet when I'm in Windows

I have an iMac Intel 2.4 GHz, 20" monitor, 4GB RAM, 320 GB HD, and when I'm running Leopard my internet works fine. But in Windows (bootcqmp0 I didn't succeeded to set the internet connection. I have a cable modem connected directly to the ethernet port. When I check my connection in Windows, appears a message saying I have a problem in my connection; but it's the same connection I use with Leopard.
How can I solve this?

You should check the Device Manager and make sure the ethernet driver is installed (it is part of Boot Camp). If the driver is installed and not giving any errors, you should see if your Windows is getting an IP address from the cable modem (in different Windows the GUI method is a little different, in any Windows "ipconfig" at a command prompt will give this info).

Did you insert your Leopard disk with Windows running after you installed Windows in Boot Camp? Try that if you haven't - that's what installs all the relevant device drivers. Also, although you indicated you had the modem connected directly to your computer, Boot Camp installs sometimes have difficulty sorting through the security/encryption protocols that some routers and firewalls use. Try disabling security on your connection (even though that leaves it wide open temporarily) and see if it gets recognized. One of those two things is likely to solve it for you.