...try the recycle bin if it might be there, it might be accidentally deleted,, or if you know the program/ program provider, you can find the original icons under "program files" in the c: drive,, don't move these icons rather just create a shortcut on the desktop,
or you can also find them in the start menu,,
...if not you can use system restore to undo the changes made to your computer but you have to first check for programs that can be affected during the process,,
...else, it might be other problems concerning your pc, might be a virus, or others,,