Windows 7: desktop icons keep moving....

Every so often i find that my desktop icons have moved from where i positioned them. The right click menu for auto arrange icons and align to grid are both unticked. My wife uses PC as well but she doesnt move them!
I dont understand how Windows 7 might be moving them! i have AVG free, Spyware doctor and WIN 7 firewall all operating and never usually have any probs but theres a worry in the back of my mind that it could be an infection that is causing this as a "joke" virus.?

or is it something to do with Windows 7 ? !!
its not drastic but just really niggling me!!
sorry but i havent actually checked whether theyre being re-arranged in any sort of order.



Thanks for any ideas!

You might try the FREE version of MalWareBytes for spyware.

Run it in Windows Safe Mode for best results.

It is unlikely that a virus does that. But running AVG and Spyware Dr. together (if they are both active) is not such a good deal.
I myself do not like Icons on my desktop. I hide them in Rocket Dock and in Toolbars. There they cannot move around.

I usually have just the Trash and one other program on my desktop. But when I'm building a new theme there's images and IE shortcuts and all sorts of stuff on there!
So to keep it in order I use and have used for aeons Jamie O'Connells Desktop Restore. Adds itself to your desktop context menu. There's a 32 or 64bit version.

As to why they move about, it's a little known feature added just to annoy you!! (In other words, I dunno!)