I use Win7 Ultimate, and haven't seen this happen. I don't let Windows remove "unused icons" to begin with.

If I were you, I would do a Control A on the desktop, to highlight all of the icons, then do Control C to copy them. I would then open a new folder on the desktop and call it something like "Icons" and I would then paste all of the copies into the folder. And there they are as a backup if you lose them from the desktop.

SRS