Here's more detail, in case it helps anyone with a similar problem, because I would have lost a lot of my family's e-mail without the fix posted above by Taurarian.
The system is a Dual-core intel CPU, multiple HD main family computer running Win XP, with four family accounts, 3 of which are using Outlook Express for their e-mail. Had a virus attack and mess up the system, but wasn't too concerned becasue it has Acronis Tue Image running system back-ups every few weeks and an external HD backing up the data files as well.
Running Acronis to restore, turned out most of the more-recent back-ups were not "valid" to be able to do a system restore, had to use one from about 6 months back. No problems, I though, since I have a secondary back-up of all data files, and no significant software installations in the past 6 months. So restored the system with Acronis, then updated the data folders from the data back-up, only a few days old. Everything seemed to work fine. Outlook Express on the system admin Windows account worked fine, but OE would not run on the other two Limited ( kids ) accounts, the "could not access the message store " etc problem.
I tried a multitude of fixes, including uninstalling and re-installing IE 7 ( and OE I assumed ) - no effect, same problem with OE not running on the Limited accounts.
Checked write protection on the OE messge store files, nothing write protected, but these files were somehow "locked" in that there names could not be changed ( file in use type message ), although they could be copied, and the copies were name-changeable.
Messed around too long trying to export the message store files using OE on the operable admin account and import into Outlook ( also on this machine ) but could not find an easy way to do this OE - O export-import across a two accounts.
I found this fix a while ago, but at first couldn't make it work. When running an Install on ie.ini, first window to pop up was a reqeust to load iexplorer.exe from the Windows system disc. This didn't work I think becasue this file is actually compressed on the system dics.
I was running this ie.ini Install on one of the kids limited accounts, and realized it may be blocked by the limited functionality of the account, so switched the account to admin permissions. Then I started searching for the iexplorer.exe file that was already loaded on C:, the Installation program seemed to realize it already had what it was trying to load, so I hit the Ignore and Continue buttons through a long list of files already loaded, occasionally needed to search and point to system files already loaded, eventually the Install ends, re-boot and PRESTO, Outlook Express runs on all three accounts - Huge thanks to Taurarian for this fix !!! This guy ( gal ? ) knows what makes OE tick !