Author: Tomas Rutkauskas 

How to find how many (or is) users are connected to Access DB

Answer:

You can do it by using ADO components. Put TADOConnection and TADODataSet 
components on the form and name it ADOConnection1 and ADODataSet1. Information 
about users will be handle in ADODataSet1 then ADOConnection1 become active. More 
about ADO schemas you can find in 
MSDNhttp://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnimo01/html/o2
k0135.asp.
1   
2   ADOConnection1.OpenSchema(siProviderSpecific, emptyParam,
3     '{947bb102-5d43-11d1-bdbf-00c04fb92675}', ADODataSet1);