DOS based to Windows Programming

I have been developing embedded systems for many years in 'C' and developed a serial interface to our products thru a DOS based system many years ago. This DOS based system runs on WinXP and Win2000, but is a bit slow due to the slow BIOS conversions. It is time to convert over to a true Windows platform. Any ideas on what I should use? The DOS platform is written in true 'C', so I was hoping to reuse some of the software and just rewrite the drivers. That might be wishful thinking. I thought about Visual C++ 2005 since I might be able to reuse some of the code, but I'm not savvy in OOP. Can anybody give me any pointers/tips/options on which way to go? Thanks.

Sutton