Windows 7 icons rearrange themselves
Solution 1:
Get DesktopOK - it will save and restore the positions of icons.
DesktopOK is freeware, works for Windows Server 2000/2003/2005 and Windows 98/XP/Vista and Windows 7 32-bit/64-bit.
Alternatively, try this Vista 'registry hack':
Save and Restore Desktop Icon Layout in Windows Vista