TuneUp Utilities is one of the best system optimization suite for Windows. It provides various options to tweak your system. It also provides options to change Windows theme, boot screen, login screen and icons.
Here is a step-by-step procedure to change or create new boot screen in Windows XP and Vista using TuneUp Utilities:
1. First download and install TuneUp Utilities from the following link:
Download TuneUp Utilities
You can either purchase the full version or download 30 days trial version. After installation, run it from desktop or from Programs menu or by right-clicking on My computer icon and select "TuneUp Utilities".
2. Now click on Customize Windows ->  TuneUp Styler

3. It'll open a new window. Click on "Boot Screen" link in left-side pane:

4. Now click on "Add -> Load Boot Screen From File..." option:

5. Select your boot screen file and click on "Install Boot Screen" button:

6. You can also create your own boot screens. To create new boot screen, click on "New Screen" button. It'll open a new window. Now click on "Search Local Drives" link and select the image.

You can also set the image alignment, borders, background color and progress bar position.
7. Once you finish, click on "Save boot screen" link and provide a name to your boot screen.

8. You can even see the preview of the boot screen by clicking on "Show large preview" link or by clicking on the image in Preview pane:

9. That's it, your new boot screen is ready. You can apply it by clicking on "Install Boot Screen" button.