Hi eg0head
Here is an XP walkthrough on how to check if your modem is installed or the drivers are corrupted (nothing to worry about )
Select the control panel classic view ->System->Hardware->Device Manager->Check Network Adapters or other devices.
There should be an Ambit modem in one of these, if either has any errors on it i.e yellow question mark or exclamation mark then right click the modem make sure you have the CD in the drive and USB cable plugged in .
From the small menu select Update Drivers and if it asks to connect to the internet say No not at this time and follow this Automatic install option.
When it has finished installing the modem should now be found in Device Manger without the error. If it is go to Network Connections in the Control Panel and check if you have a Local Area Connection enabled with modem name on it
If so right click the icon and Select Status->Support and check the IP address the last number of that IP address should end in a number between 248 and 253.
Close Control Panel and make sure any Anti Virus and firewalls are off, it is safe. Open Internet Explorer and type this IP into the address bar 80.5.178.26 you'll either get a Security alert or the registration screen.
Accepting the alert screen will get you to the registration screen as well. Check Robin Walker's site on this forum also if you get stuck.
If you get to your personal details page it takes about 5 minutes from there to complete registration. You will see a screen at the end informing you that the modem will reboot, before going on the web make sure you enable your Anti Virus and Firewall a reboot of your PC should sort that out
Check for any updates and download them
P.S. Sorry it's the clocks going back nearly forgot
If you don't have the errors I mentioned go from checking the IP address part of this post