I linked to some information on running Windows XP (2000/2003 as well) from a limited (i.e. non-Administrator) account last year. Today I’ve found Aaron Margosis’ pages on this topic to be extremely helpful on this topic. For example:

Here’s an odd little one you might not have noticed. The Windows Calculator applet remembers whether it was last displayed in “Standard” or “Scientific” view, and whether digit grouping was selected, and restores those settings the next time you use it. Because this applet dates back to the very early days of Windows, it saves these settings in the win.ini file in the Windows folder. There are two problems with this: 1) the settings apply to all users of the computer, and 2) you need to be an administrator to write your settings into this file. Likewise, the Character Map applet remembers the last font and codepage selected, and whether “Advanced view” was checked – but only if the user is an admin.