Check Windows support for information on general network troubleshooting.
Make sure you have the right ports open to connect to LIVE.
Make sure that your firewall and security settings allow your PC to connect to Xbox Live. If you use a firewall other than Windows Firewall, contact the software provider for details about how to connect to Xbox Live.
Games for Windows LIVE-specific troubleshooting
Find out what to do if you have problems signing in to Games for Windows Marketplace.
Learn about possible solutions for connection issues if your Windows-based computer can’t connect to Windows LIVE.