Making some tests in Windows XP for customizing a user interface in QGIS 1.8 (see http://www.duif.net/qgis/doc/output/html/en/docs/user_manual/introduction/qgis_configuration.html#customization), I have unchecked, among other options, the Settings Menu. This means that, after restarting QGIS, there's no way of recovering the older settings because there is not already a Setting Menu. So, I cannot reload any ini file.
For your information, as a precaution, previously I have saved in a folder both the original ini file, with all the options, and the customized ini file with only some options (of course, not included here the necessary Settings Menu).
Before reinstalling QGIS (version 1,8), I would like to try other smarter options if there's any. Where and what does QGIS look at where this applications starts?