If a version came with your computer, thats the one for your system. Manufacturers dont put 32 bit OSs on 64 bit computers. If it came with a 64 bit OS, you could, nonsensically, install a 32 bit, but don't. Just don't. If it came with 64, then go buy a new 64 bit OS. BTW, based on your question exactly, there is no conversion from one to the other.