i'm getting error message- you can't change the icon of executable files

[elisa.luv]

hi~

i don't know anything about computers....
i have windows xp...
i used Ad-Aware SE Professional program this morning and i deleted some files then suddenly all the icons from my desktop dissapeared!!(ex. itunes.lnk) and when i double click to open the
program, i get error message says that - you can't change the icon of executable files...

please help me~~ i don't know what to do...