Downloaded free screensavers to desktop, how do you send them to your screensaver file

Next, you need to apply the Screensaver settings to the Logon Desktop / Welcome Screen (Technically, HKEY_USERS\.Default registry key), so that the Screensaver is invoked when no user is logged on. Copying all the Screensaver settings to the Logon Desktop (or Welcome Screen) manually is a tough task. Use Tweak UI instead.
Download and install TweakUI.
Launch TweakUI and click Logon, click Settings.
Select Screensaver from the list box and choose Copy Now
The Screensaver settings are applied to the Logon Desktop
Restart Windows for the changes to take effect
Allow few minutes at the Logon screen, to test if the Screensaver is working properly. The Screensaver should launch after the timeout. It will look as if the Company Logo moves around.
Additional Tip
The User interface / slider allows the minimum value for picture change interval to 6 seconds only. To reduce the change interval to less than 6 seconds, alter the registry value named ChangeInterval (Set decimal value 1000 for 1 Second, and so forth) in this key:
HKEY_USERS \ .DEFAULT \ Control Panel \ Screen Saver.Slideshow
For Current user profile, make the change here:
HKEY_CURRENT_USER \ Control Panel \ Screen Saver.Slideshow

With no logon wallpaper set, Windows displays a pre-defined color for the logon desktop. ( If you have enabled Welcome Screen, press CTRL+ALT+DEL twice to see the logon screen background color. ) To change the logon background color to that of your choice, you need to alter the registry:
Click Start, Run and type REGEDIT and press Enter
Navigate to the following key:
HKEY_USERS\.DEFAULT\Control Panel\Colors
Backup the registry key by exporting to a REG file
In the right pane, double-click Background
In the Edit String dialog box, type the Color code in R G B format and then click OK.
Example: Type 0 0 0 if you want to see a Black background. You can choose any combination from 0-255
Points to ponder
If the logon Wallpaper is set, the background Color may not be visible. So, you must reset the Wallpaper value to a blank string in this key: HKEY_USERS\.DEFAULT\Control Panel\Desktop
If the Background value is set under the following Winlogon registry key, the above setting is ignored. In other words, the Winlogon\Background value takes precedence over the .DEFAULT..\Background value.
HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon

Make use of the Windows XP's My Pictures Slideshow screensaver for this purpose. Follow the steps:
Using Paint brush (mspaint.exe), create 10 or more images with a Black background in each. Open each image file and embed your company logo in it, in (place it in random areas, one in each image).
Create a folder for the image files you've created, and place the images in that folder. Assign this folder read-only permissions for all the users.
Now, configure the screensaver under your user profile. In the My Pictures Screensaver properties, do the following:
Set the folder where you've stored the image files
Set the interval using How often should the pictures change slider.
Uncheck all the checkboxes at the bottom of the dialog
Click OK and save the changes
Set the Screensaver Timeout to a preferred value in minutes
Test the Screensaver in your profile to see everything is fine