Multi-users editing same record at the same time?

I am having a problem with multiple users accessing and editing the
same record and the same time.
I am using Paradox tables.
All the computers accessing them are using the same drive letter,
and have the netdir set to the same file.  The share is set to true
on all machines.  The error I get is that there are multiple .net
files in use, yet there is only one in use.
Can someone please tell me how to get this multi-user thing to work

Also I have some old Foxpro files that I need to convert to Paradox and
when I try to open them I'm told that the indexs are corrupt or missing.
When I try to open the in the Database Desktop I get the message
Production Index file missing, corrupt or cannot interpret index key.
then I'm given the option to:
   Open read only
   Fail Open
   Convert Non-DBase Index
Now these files are a little on the old side (think they are Foxbase)
How can I produce what the Database desktop is doing?
Thanks
Robert Milmine