1) Go to
ThemeXP.org and download a simple looking theme. I used
this one.
2) Extract the exe from the zip file and open it with
Resource Hacker.
3) Expand the Bitmap section, expand the folder 100, and select the 1033. You should see the background image in the right panel.
4) Right click on the image and hit copy.
5) Open Paint and hit Edit->Paste. Select Image->Attributes and take note of the size and the dpi. If you have chosen a good starting logon this should be the same size as your desktop.
6) Choose a good picture of you girls. Resize this image so it is the same as the one being replaced. DPI should be the same as the one being replaced or just use 72 dpi.
7) Return to ResHacker with the background image still selected. Select Action->Replace Bitmap. Open your picture and hit Replace. If you get an error here, try resizing the image with a different program. If I use Photoshop 5 to resize this step will always fail.
8) Select Save As and name the file logonui.new.
9) Move logonui.new to C:\Windows\System32
9a) Copy logonui.exe and name the copy logonui.exe.bak.
10) Restart your computer and hit F8 during boot to get the safe mode menu. Choose ?Safe Mode with Command Prompt?.
11) Log on with administrator privileges. At the prompt type
cd c:\windows\system32(enter). Then type
copy logonui.new logonui.exe(enter).
12) Restart your computer and you will see your new logon screen.
Standard disclaimer. I originally got this info from
bfarber
Edit: This is how to do it without any 3rd party apps. There are programs to make this easier but I have never used one. There should be more information on these programs on ThemeXP if you are interested.