Flash drive speed

Hello dear iron lovers!

Problem

On the network, it is impossible to find information about the speed of a specific model of USB Flash drive (in common people flash drives). The reason for the secrecy of this information is not known to me.

Our decision

A utility was developed to test the flash drive and send the results to the site.

Benchmark

The application is written in the .NET Framework 2.0. For low-level operations, a .dll module is written in C ++.
The goal was to evaluate the speed of reading and writing to a card blocks of different sizes. To solve this problem, I used the WinAPI functions: CreateFile, WriteFile and ReadFile. When creating the file, the FILE_FLAG_NO_BUFFERING flag was set, which indicates to the OS that you should not use any kind of file cache.
Here is the test for writing blocks:

__declspec(dllexport) double WriteBench(LPCSTR path, long size, long count, char* ErrorMessage)
  {
    HRTimer timer;    int i;
    double elapsed;
    HANDLE hFile; DWORD dwResult;
    void* buffer = malloc(size);
    memset(buffer, -1, size);
    hFile = CreateFileA(path,
              GENERIC_WRITE,
              FILE_SHARE_WRITE,
              NULL,
              CREATE_ALWAYS,
              FILE_FLAG_NO_BUFFERING,
              NULL);

    if (hFile == INVALID_HANDLE_VALUE)
    {
      sprintf((char*)ErrorMessage, "Could not open file (error %d)\n", GetLastError());
      return 0;
    }

    timer.StartTimer();
    for (i =0 ; i< count; i++){
      if(!WriteFile(hFile, buffer, size, &dwResult, NULL))
      {
        sprintf((char*)ErrorMessage, "Could not write to file (error %d)\n", GetLastError());
        return 0;
      }
    }
    elapsed = timer.StopTimer();

    CloseHandle(hFile);
    DeleteFileA(path);
    free(buffer);
    return elapsed;
  }

* This source code was highlighted with Source Code Highlighter.

I would be very grateful if you look at my UsbFlashSpeed.com project and point out the discovered flaws.
This post is for pre-testing the service and collecting criticisms! The announcement of the service will be later.