首先制作一个能改变屏幕分辨率的C#程序，源代码如下，使用了VS.NET 2005 BETA 1：
1、新建Windows Application工程，取名为ScreenResolution
2、粘贴各文件的代码：
Program.cs

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#region Using directives

using System;
using System.Collections.Generic;
using System.Windows.Forms;

#endregion

namespace ScreenResolution
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.EnableRTLMirroring();
Application.Run(new Form1());
}
}
}

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Form1.cs

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using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;

namespace ScreenResolution
{

partial class Form1 : System.Windows.Forms.Form
{
public enum DMDO
{
DEFAULT = 0,
D90 = 1,
D180 = 2,
D270 = 3
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
struct DEVMODE
{
public const int DM_DISPLAYFREQUENCY = 0x400000;
public const int DM_PELSWIDTH = 0x80000;
public const int DM_PELSHEIGHT = 0x100000;
private const int CCHDEVICENAME = 32;
private const int CCHFORMNAME = 32;

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHDEVICENAME)]
public string dmDeviceName;
public short dmSpecVersion;
public short dmDriverVersion;
public short dmSize;
public short dmDriverExtra;
public int dmFields;

public int dmPositionX;
public int dmPositionY;
public DMDO dmDisplayOrientation;
public int dmDisplayFixedOutput;

public short dmColor;
public short dmDuplex;
public short dmYResolution;
public short dmTTOption;
public short dmCollate;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHFORMNAME)]
public string dmFormName;
public short dmLogPixels;
public int dmBitsPerPel;
public int dmPelsWidth;
public int dmPelsHeight;
public int dmDisplayFlags;
public int dmDisplayFrequency;
public int dmICMMethod;
public int dmICMIntent;
public int dmMediaType;
public int dmDitherType;
public int dmReserved1;
public int dmReserved2;
public int dmPanningWidth;
public int dmPanningHeight;
}

[DllImport("user32.dll", CharSet = CharSet.Auto)]
//static extern int ChangeDisplaySettings( DEVMODE lpDevMode, int dwFlags);

static extern int ChangeDisplaySettings([In] ref DEVMODE lpDevMode, int dwFlags);
//private System.ComponentModel.Container components = null;
public Form1()
{
InitializeComponent();
}
// protected override void Dispose(bool disposing)
// {
// if (disposing)
// {
// if (components != null)
// {
// components.Dispose();
// }
// }
// base.Dispose(disposing);
// }

#region Windows Form Designer generated code
// private void InitializeComponent()
// {
// this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
// this.ClientSize = new System.Drawing.Size(292, 273);
// this.Text = "改变屏幕分辨率的例子";
//
// }
#endregion

// static void Main()
// {
// Form1 r = new Form1();
// r.ChangeRes();
// Application.Run(new Form1());
// }

void ChangeRes(int chMode)
{
Form1 t = new Form1();
long RetVal = 0;
DEVMODE dm = new DEVMODE();
dm.dmSize = (short)Marshal.SizeOf(typeof(DEVMODE));
if (chMode == 1)
{
dm.dmPelsWidth = 1600;
dm.dmPelsHeight = 1024;
dm.dmDisplayFrequency = 85;
}
else if (chMode == 2)
{
dm.dmPelsWidth = 1024;
dm.dmPelsHeight = 768;
dm.dmDisplayFrequency = 85;
}
dm.dmFields = DEVMODE.DM_PELSWIDTH | DEVMODE.DM_PELSHEIGHT | DEVMODE.DM_DISPLAYFREQUENCY;
RetVal = ChangeDisplaySettings(ref dm, 0);
}

private void Form1_Load(object sender, EventArgs e)
{
ChangeRes(1);
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
ChangeRes(2);
}
}
}

3、在Design视图下将WindowsState设置成Minimized，ShowInTaskbar设置成False

其次根据每个用户的需要修改ChangeRes方法里对分辨率的设置，生成工程后将可执行文件放在此用户的启动文件夹内

总结：
程序的原理很简单，在用户登录时将分辨率设置成用户的期望值，程序在用户登出前始终运行，但用户不会察觉，在用户登出时，程序被终止，分辨率被设置回特定值，以此实现统一登录分辨率并且各用户有自己的分辨率。

改进：
如果用户较多，可以通过程序参数来改变屏幕分辨率，避免多次生成工程并产生多个版本的混乱。

测试平台：
Windows Server 2003，Visual C# 2005 Beta 1