Network connection problems in Windows tutorial is designed to 'help you identify and fix network connection problems in Windows. This tutorial doesn't cover network connection problems related to specific programs. Network connection problems can be caused by cables that aren't connected properly, corrupt drivers, incompatible drivers, network connection settings, missing updates, and hardware or software problems."
It's split into 3 sections and covers Windows 7, Windows Vista and Windows XP:
- Check your hardware, cables, network adapters, modems etc. are all connected and working correctly
- Try one of the inbuilt troubleshooters such as the Network troubleshooter
- Make sure all your drivers are up to date
Here's the full guide: