I will refer to 'Cubase' when I mean the sequencer/digital audio recording software Cubase VST, Cubase Score VST, and Cubase Studio VST. The information is probably valid for all versions of Cubase (I used Cubase Score VST version 3.55). I use Windows 95 on a PC.
For Windows 95/98, there is a demo version of Gemulator Explorer that will do the job (download it here).
You will probably have to rename some of the files. For instance, file names containing a "*" (star) are not valid on the PC.
The main Cubase song file is the easiest. Simply add the extension ".all" to it, and Cubase can read it.
Now, for the audio files, things are a bit more complicated. Cubase on the Mac can read several formats that Cubase on the PC cannot. To find out what kind of file it is, the simplest is to use right-click in Gemulator Explorer.
Usually it says AIFF which means it is a file in Audio Interchange Format. Simply add the extension ".aif" to the file to make it readable in Cubase (Note: Do not use the extension ".aiff"; Cubase will not be able to read the file correctly).
Gemulator explorer may also report the file is of type Sd2f. This is a Sound Designer II file. It cannot be read by Cubase but have to be converted first. Any sample converting program will do, for instance, the shareware sample editor AWAVE (download it here). Convert the file to AIFF or WAV and Cubase will be able to read it.
You should be able to convert any other potential formats you encounter using a sample converter.