-_- Seriously? Old Borland Turbo C? Well if you really need to you're best off either downloading XP mode and installing it there, assuming you have W7Pro like I do, or installing a copy of XP (or even heaven forbid Windows 9x) on Virtual Box in a VM.
Keep in mind that the software is old stuff. If you want to use it school programs you write and compile in Turbo C will not automatically compile with something like Microsoft's Visual Studio C++. Now assuming you're not using the OWL library the differences are generally just how you include libraries, but a few functions will behave slightly differently. Remember a lot has changed in all those years