This is an access rights issue, and you will probably only experience it when your log into an PC (W2K or XP) with normal user rights rather than administrator rights. To solve it, log in as an Administrator, and then carry out one or both of the following steps:
i) run the programme Regedt32 from your Start / Run menu. This is a more powerful registry editor than Regedit. Select the window for 'HKEY_LOCAL_MACHINE on Local Machine' then browse to the key '\SOFTWARE\BORLAND'. You now need to set the Security Permissions for this key to be Full Control for all users. Check the help on how to do this because it varies for the operating system; for example, with W2K there is a Security main menu.
ii) search for the file IDAPI32.cfg in 'C:\Program Files\borland\...' When you find it make sure that it is NOT read only and that again, all users have full control.
You may find that performing step i) alone is sufficient to solve this problem. To test, log back in as a user and try to select a Company in the Eclipse Multi-Company programme