i have found this and it works for me ,i just thought of sharing this
Your problem is not with "iw3sp.exe". That's the demo executable. Chances are, your problem is with a file called "mssmp3.asi". It has something to do with the sound handling. Not sure what it does, but apparently, it's not necessary to run the game. I re-named the file, and I don't get the crash anymore. Presumably, you can delete it, but I simply chose to re-name it just in case.
Go into your CoD4 Demo installation folder. Go into the "miles" sub-folder. It should look something like:
c:\Program Files\Electronic Arts\C0D4 Demo\miles
Locate the file: "mssmp3.asi"
Rename it: "mssmp3.bak"