Save these instructions somewhere safe and close Chrome:
- Open (XP) "/Users/[your user name]/Library/Application Support/Google/Chrome/Local State (Vista/7) "C:\Users\[USERNAME]\AppData\Local\Google\Chrome\Local State" in Notepad
- Search for the line "extendedreach": true using Ctrl-F
- Delete this line and Chrome will start to prompt you to open extendedReach links again