How to lock/pin desktop icons once they are arranged?

Hi, does anybody know of a way (in Windows 7) to lock/pin the desktop icons in place
once you have arranged them?

My desktop isn't exactly cluttered, I don't think, there are at any given moment some 45-50. For
the sake of easy navigation I try to keep the number to a minimum.

When I have moved the icons around so that they are grouped into categories (roughly)
and have their fixed places, it's easy to find what I'm looking for, and one gets used to it,
like the layout of ones apartment for example. The desktop 'feels like home' to put it
simply, plus it looks good.

But every once in a while upon boot they are moved to the left side of the screen, not
sorted alphabetically (which, at least, would have been some help) but in completely
random order so it takes unnecessarily long to find what youre looking for.

I would understand it, and accept it, if it ocurred only after I, say, change the resolution,
but it happens randomly, 'unprovoked'.

Not a big problem, granted, but kind of a drag, so if anybody knows how to pin/lock the icons
in place I'd be very grateful to know how.

Thank you!

I am a poor example, as I only have three icons on my dektop. But I presume you do have the right click options View - "Auto arrange icons (switched off) and "Align icons to grid"

Yes Sir/Mam, I do. Also, I think three or thirty-three icons doesn't matter, the principle's the same.