C++ :: Parsing A Large File Into Smaller Units

I have a large binary file (84GB) that needs to be broken down into smaller file sizes (~1GB to 8GB) for analysis. The binary file is on a 32-bit machine and cannot be copied to another machine for analysis. The PC has Visual Studio 6.0 and is not upgradable. My issue is I'm using the following generic code to create the smaller files.

fseek(file, start, SEEK_SET);
end = start + (variable based on file size);
fseek(file, end, SEEK_SET);
for (i=start; i<end; i++) {
if(!feof(f)) {
byte = fgetc(f);
fputc(byte,new_file);
}
}

However, on a 32-bit machine, the iterator can only count up to ~2billion. Which means that I'm unable to copy anything past ~2GB. My original idea was to delete from the large binary file as I read from it so that I can reset the iterator on every read. However, I haven't come across a way to delete binary file entries.

Is there any other way that to break down a large binary file into smaller units? Or is there a way to delete binary file entries in sections or per entry?

On a 64-bit machine I could use _fseeki64. I've been reading that some versions of Visual 6.0 are capable of supporting 64-bit numbers but when using _fseeki64 or _lseeki64 on this machine its an "undeclared identifier"