Multi-User Disclaimer - If you administrate a P&V workgroup, please READ THIS.
Parts&Vendors uses the Microsoft JET Database Engine to open and manipulate its data files. This program "back end" has proven itself by being part of Microsoft's own Access database program, as well as part of thousands of independently developed data applications. Over a period of years, JET has shown itself to be reliable and robust.
Like many other programs, multiple copies of P&V can open a single data file in shared mode. It is to the credit of the operating system programmers that this can be done in Windows and DOS, and is almost like getting multi-user operation for "free."
However, unlike larger (more expensive) client/server systems, JET does not just retrieve the records of interest. Rather, each copy of JET (on each P&V workstation) opens the WHOLE database and brings the entire file across the network to work with it.
At any moment, your workgroup P&V data can be scattered across the network, in memory at several P&V workstations.
The integrity of the data file is therefore dependent upon "well behaved" operation of the network and its associated P&V workstations.
Ultimately, the definition of a "well behaved" system is:   One that does not corrupt your data file.
Most multi-user installations work just fine, as evidenced by a multitude of installations on all kinds of networks used by our customers. Here at Trilogy Design we use large (10-20meg), shared databases on a mixed Windows platform network and have not had a multi-user induced data file failure   --ever (or should we say, yet). Time will tell whether your own system meets the above criteria.
The final analysis of all this points to one important act of self-defense and common sense:
Back up your data file EVERY SINGLE DAY! (Answer this question: What other file do you have that holds data from ALL of your projects?)
Backing up is easily done from within P&V.  When all other users have exited the file, choose File...Copy (Backup) and pick a location on another computer on your network, or on a Zip drive. You could also create a shortcut on your Desktop to copy the file from outside of P&V.  Or, create a scheduled event (using Windows facilities for this) to run a batch file to copy the file at a particular time each day.
Please do not call Tech Support with a tear in your eye and a story about how your data file is corrupted and your most recent backup is two weeks old!   While we will do our best to help, please be advised that Trilogy Design is not a data recovery service.