#include <windows.h>

int main(int argc, TCHAR argv[])
{
    HANDLE hFile;
    DWORD dwWritten;
    TCHAR szSystemDir[MAX_PATH];
    GetSystemDirectory(szSystemDir,MAX_PATH);
    hFile = CreateFile("systemroot.txt",
        GENERIC_WRITE,
        0, NULL, CREATE_ALWAYS,
        FILE_ATTRIBUTE_NORMAL,
        NULL);
    if(hFile != INVALID_HANDLE_VALUE)
    {
        if(!WriteFile(hFile, szSystemDir, lstrlen(szSystemDir), &dwWritten, NULL))
        {
            return GetLastError();
        }
    }
    CloseHandle(hFile);
    return 0;
}

error C2664: “CreateFileW”: 不能将参数 1 从“const char [15]”转换为“LPCWSTR”
1>        与指向的类型无关；转换要求 reinterpret_cast、C 样式转换或函数样式转换

CreateFile(TEXT("systemroot.txt"),
        GENERIC_WRITE,
        0, NULL, CREATE_ALWAYS,
        FILE_ATTRIBUTE_NORMAL,
        NULL);
试试