Win7 XP Mode: How can 2 different Win7 users access same files on C:?

I have an application that requires XP Mode (Virtual Windows) because it will not run under Win7 natively. It is used by multiple Win7 users. It uses a shared database which must be located on C: -- and the drive letter is hard coded into the program.

The problem is that each Virtual XP machine has its own private C: drive. How can I finagle things so these different Win7 users, with distinct Win7 login identities, can share files on what appears to be C: ?? (without upsetting the virtual WinXP OS)

Oh yes ... these Win7 users must be easily able to take the result files produced by this program and use it with their native Win7 applications and files. And, no, the Win7 users cannot share a Win7 login, because they each have different files which are confidential.

I'm stumped. Please help!
Rainer