Yep, as Mr. King says - you may have your desktop icons set to automatically arrange. If they are automatically arranged, they have been stacked in the upper-left corner and locked in placed.
To unlock the icons so that you can move them again, clear the check mark next to Auto arrange icons (as King has showed you) and you should have full management of your icons.
Let us know what happens.
Cheers,
Cassandra
Microsoft Windows Outreach