Problem symptoms:
A 32 bit screensaver is installed without problems on Vista 64 bit, but does not appear in the list of installed screensavers, in the display properties.

Also, when clicking the screensaver icon on the start menu, windows says "the shortcut  has been changed or moved" and asks if you would like the shortcut removed.

Background information:
On 64 bit windows, screensavers of 32 bit are installed in the folder 
c:\windows\SysWOW64

The screensaver folder on a 32 bit windows would be:
c:\windows\system32

Screensavers have the extension ".scr". For example the starmessage screensaver has the name of starmsg.scr

Troubleshooting help:
Even if you are using a 32 bit screensaver you can try the following tricks to make it work:

Copy the screensaver "starmsg.scr" from
c:\windows\SysWOW64
to
c:\windows\system32

See if this makes the screensaver appear in the screensavers list.
If yes, press preview to see if it operates normally.
See if the start menu icons are now working ok (not being reported as broken shortcuts).

Otherwise, right click on starmsg.scr in the folder c:\windows\SysWOW64 and select install.

See if this makes it appear in the screensavers list.
If yes, press preview to see if it operates normally.
See if the start menu icons are now working ok (not being reported as broken shortcuts).

Update:
The screensaver setup versions 4.14 and later are compatible with the new 64 bit windows (Vista 64 bit, 64 bit Windows 7).