This is my current desktop with a moving waterfall wallpaper thanks to the Dreamscene patch for Vista which lets you view wmv as wallpapers...
Dreamscene patch for Vista Home Premium and Business get it here [link]

Instructions:
for those of you newbies first dl Takecontrol from here [link] so you won't have to go trough all the steps of clicking a billion times simply to rename the files then
Download the patched DreamScene files as above and unpack to a folder.
Copy " DreamScene.dll to %WinDir%\System32\ " folder.
Copy "DreamScene.dll.mui to %WinDir%\System32\en-US\" folder.
In Windows Explorer, navigate to "%WinDir%\System32\ " folder.
Right click on themecpl.dll file and take ownership, then Rename the file to themecpl.dll.original.
Copy the patched version of themecpl.dll to "%WinDir%\System32\" folder.
Repeat on "themecpl.dll.mui " file located in "%WinDir%\System32\en-US\" folder.
After taking ownership, rename the file to "themecpl.dll.mui.original".
Copy the patched version of "themecpl.dll.mui" to "%WinDir%\System32\en-US\ " folder.
Create a new folder in "%windir%\Web" named "Windows DreamScene" (without quotes). This is the location to place all the videos you want to set as DreamScene wallpaper, and can be easily configured via Control Panel Personalization applet.
Lastly, import and merge DreamScene.reg to registry. (rightclick file and click on merge)
Reboot computer.
Using DreamScene

After patching, right click on any blank space on Desktop, select Personalize, then click on Desktop Background. Under location, select Windows DreamScene Content and then select an animated video you want.

Download dreamscene videos from here [link]
this dl includes these videos:
Waterfall
Aurora
Glacier
Lake
Greenery

Dreamscene for XP can be found here [link]