Alternative to using stardock
If you didnt want to use stardock then you can edit the imageres.dll located in the windows\system32 folder. Take a copy of it and work from that. You'll need a resource editor. There are loads if you google it.
When you open the imageres.dll you'll see a section called IMAGE and under that there will be codes that start with 5031 down to 5043. Inside each one is the bitmap image for the logon screen. Each code represents the different screen resolutions the image needs to be saved as and has to be a bitmap. Upload your new image and save the file out and all done. You'll need to copy the file back (after backing up the original of course) and you'll need to have special permissions on that file to do it.
Bear in mind that any service packs that come out may end up overwriting the file so keep a copy or redo the changes with the newer file.
