<p>We're doing an "Amazing Race" kind of event, and thought it would be cool to have CDs that could only play once... like a "this message will self destruct in 5 seconds..." </p>

<p>Any thoughts on how to do this?  I was thinking it could be a compiled HTML website that would write a cookie and only play once.  I don't want to write to the registry (don't want to depend on windows, don't want to install anything, etc).</p>

<p>I also don't care if it's hackable... This is a one-time fun event, and I don't really care too much if people could remove the cookie or something.</p>

<p>Any other ideas?</p>

If the content is HTML and run inside a normal browser window, then a cookie may work but there are caveats:
User runs the CD once when IE is the default browser. User runs at a later time, when Firefox is the default browser so cookie cannot be checked.
The browser's security settings may be locked down to prevent use of script so the cookie cannot be set (more of an IE problem).
An alternative might be Flash's equivalent of cookies, but if script was locked down then the same may be true for Flash.