1. The PCMag article (second page) [AutoWhat? 2] explains that each input field in a Web-based form has an internal name that identifies the field to the system. When you submit the information in the form, IE records each input field's data in the Registry in a list associated with the particular field name. The next time you start typing in a field that has the same internal name, whether on the same Web page or a different one, IE will pop up a list of previous values that begin with the text you've typed up to that point. You can click on one of the items to select it, or press the Down Arrow to select it and press Enter. If you click in a blank input field and press the Down Arrow, IE will list all data associated with that field. Under Windows 9x (95/98/Me), the internal field names are visible in the Registry, but the data is encrypted.
2. For all versions of IE except in WinME, and I don't know why not, the article [Q160158] describes two methods of behavior which can occur if files in the Temporary Internet Files and History folders, to include the Index.dat file they contain that may become corrupted and how to deal with the situation for MSN, but regardless of whether the IE version used is the MSN or not, it still applies.