The latest version of Visions of Chaos now includes both a 32-bit and a 64-bit version. You will need to have a 64-bit version of Windows to use the 64-bit version, but if you still use a 32-bit version of Windows then the 32-bit version of Visions of Chaos will continue to work for you. If you are not sure what “bitness” (bititude?) your Windows is, press Windows-Pause and look next to “System type” on the dialog that appears. Both versions are included with the same install exe to avoid confusion and the 64-bit version only installs if you are running 64-bit Windows.
The main advantage of the 64-bit version over the 32-bit is that there is no longer a 3 GB memory limit. As screen sizes have increased the amount of memory that Visions of Chaos requires to render some of its modes at these higher resolutions was hitting the 32 bit application memory limits. 64-bit Visions of Chaos can now use as much memory as you have physically installed in your PC.