by default files in the project resource are embedded in the assembly. so you can access them as byte[] using the code
[ProjectName].[Resources].[FileName]
which in your case won't work because you need the file path.So you have to explicitly tell the compiler to copy the file to the application directory. Just select the file in the resources folder, inside the solution explorer, right click and "Properties". That would give you an option "Copy to output directory" set it to "Copy always". then when you build your application it would pop up in the output directory under "Resources" folder.
Modify your code as below to accommodate the changes
string strCon ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + System.Windows.Forms.Application.StartupPath+"\\Resources\\"+[filename]+"....
hope that helped
good luck