I am using IE7 Beta2, as I said. This presumably brings its version of Outlook Express, although there are no apparent differences in OE. I do not use Outlook at all, and never have. I have not installed any recent Office versions, and I still use Office 2000, which works well. I have XP Pro SP2 with all the current updates.
When I installed Firefox, it offered me an update, which I accepted. It seemed to function well enough, until I tried to open a link in the preview pane of Outlook Express, as I have done a million times before. The same left click I have always applied now gave me my Documents and Settings folder, and when I tried other links in e-mails, again I got the Docs and Settings folder.
I restored the machine back to a date a week previously, before I had installed Firefox, and the links behaviour returned to normal. When I downloaded and installed Firefox again, the links gave me my Docs and Settings folder once more. So I removed Firefox again, and the behaviour once more returned to normal.
The conclusion I draw from this is that Firefox is causing the problem, not IE or OE or Outlook or Office or anything else that may have been on my machine for years. It seems perverse to look for problems with other programs, when all the evidence points to Firefox's being the culprit. It may be that Firefox cannot live with the IE7 Beta2, so it would be helpful to know if anyone else has this Beta installed with Firefox. I could try Firefox on another machine with XP Home and IE6, but I am reluctant to do this while it is apparently under suspicion, as I don't want two machines not working properly.
UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; SV1)