You bring your PC up to updated software levels (I mean the operating system), install a program to manage virtual images, create a virtual image where you will run another operating system (the "old" one that allows you to maintain all compatibilities with the software you desire) and old software.
When needed, you turn on the virtual image (practically a virtual PC) and use the old PC without giving up on the newest things Apple has to offer
It seems interesting, meaning a good idea, but I don't know how this virtual images thing works. I need to understand it better; do you know a program for managing virtual images? That way, by reading its description on some website of yours, I might better understand what it is about. If I understood correctly, I should create a partition on my Mac to host the old system (a bit like what is normally done when one wants to use Windows inside a Mac); right?
No, that is the case of Dual boot; instead, this is different, you have a physical image that can host N different virtual images, even with different operating systems, even running simultaneously so that data is shared and without having to turn the PC on/off... although on Mac it is very fast in terms of time.