I apologize for the double post. I feel this warrants a new post rather than an edit.

First off I have to rectify something. I said that when changing settings, the dialogs acted normally and gave no errors. This is not true for things I try to do in the dialog that you get when you right click the desktop and select Properties. I did get an error saying "Visual Style could not be loaded". However, this error does not always appear, and it didn't the first time I tried. Also, sometimes when trying to change something, that blue Please Wait message appears in the middle of the screen. However, this, too, does not happen every time.

One of the things that was wrong, which I didn't mention before, was that my Programs list in the Start Menu was empty except for an empty StartUp folder. There was no Accessories folder, as I would have normally expected. I looked in C:\Documents and Settings (this folder still exists, it is just not used in the setup my computer has), and there the All Users folder still had the Accessories folder and others in the Start Menu folder. I copied them to the D:\ drive and I now have a populated Programs list, but that of course doesn't solve my problem. It does perhaps give some hint as to what's happening. The new D:\Documents folder that XP created automatically after the format did contain an All Users folder, but XP did not recreate those Start Menu entries. Perhaps it has also failed to recreate some essential components that allow one to save preferences? Could I copy those things from another computer, perhaps? I've been fiddling with that, I copied the Local Settings folder, but that had no effect.

I've also discovered one thing I am able to change, which is the look of the start menu. I can toggle it between Classic and the regular menu.