You'll need to rewrite the code from scratch for any target.

The reason being is that VC1.52 is 16-bit code. Porting to 32-bit code may work, but you'll end up with a crappy 32-bit program.

The best thing you can do is write a detailed specification of the old features and recreate them in VC2008 or VC2010 or C#. Don't waste time writing to VC6 (a 12 year old compiler).

That way, at the end of the day, you'll end up with a modern program, not some hacked up hybrid that is difficult to maintain.