I was running Windows XP Pro x64 with SP2. Made a new partition, installed Windows 7 on new partition. On boot, I could pick Windows 7, or older Windows OS (XP Pro x64 SP2, basically Server 2003 SP2).
The Event Viewer logs events that lead to errors. The event logs can help you understand what triggered or where exactly the issue is coming from so you can be apply the relevant troubleshooting steps ...