Turbo C is a 16 bit based product. To run it in Windows 7, you need a 16 bit (DOS sized), environment.
The easiest way to do this (afaik), is to use a program like DOSBOX or VMWare. Either one (get the right product from VMWare, as they have several), will create a virtual machine for your TC program to run in.
You may be able to set up Windows 7 to work with TC, but I'm not aware of just how that would work. By all means, check via Google, and Windows 7 forums.
If you have the option to do so, now might be a great time to update to one of the newer C compilers. Some are free, also, and do offer more features.