If you haven't discovered Vista's Event Viewer yet, have a look...
1. Type "Event Viewer" in the Start menu's search box.
2. Start Event Viewer
3. Expand "Windows Logs" in the left margin, then click on "System"
This will display a log of all system events by date and time. It includes system errors.
I found that my Internet Time was not synchronizing with the PC, ever. It was showing errors since day one. Windows Firewall was blocking the port to update my clock. I had to open the Firewall settings and add port 123 (UDC) to the Exceptions tab to get it working.