Received an error while executing a Phoenix software

Hi,
I was trying to launch Phoenix software in my Win XP when I got this error message (see below).

phoenix
Windows cannot find ‘phoenix’. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.
I was very sure that it was working yesterday. Anyway, tried to look for a solution in the internet but couldn’t find an applicable one. Hope this forum could help resolve the problem.
Please help ASAP.
