It's a longshot and make sure you back up the registry key beforehand but this works in Excel 2000.
In registry, find HKEY_CURRENT_USER\Software\Microsoft\VBA\6.0\Common
Under there you should see a key called "Dock"
This appears to store the locations of the docked windows.
Should reset everything. Not sure if Excel 2003 uses a later version of VBA so may not be the correct key.
Worth a go ?