Since using a file sharing network, when playing a particular file in Windows Media Player the program closes after 30 seconds with the message that Windows Media Player has encountered a problem. I have used Norton Antivirus, Ad-Aware, and Spybot to scan the computer, and all these programs also close as soon as they encounter the particular file. This same behaviour happens in Safe Mode. The computer is running Windows XP.

File sharing networks are somewhat notorious for spreading viruses, spyware and other malware. From the description of the problem, it seems your computer might have become infected with a nasty infection from the file sharing network. Since the suspect file causes the antivirus and antispyware software to close or crash, this further indicates that the file is something not particularly nice. Therefore, you should try to remove this file from your computer as soon as possible. The first method you could try is simply deleting the file from the computer. This might work, but it may also not work if the file is in use (i.e. the infection is running on the computer). In this situation, try booting the computer into Safe Mode and deleting the file from within this mode. In any case, should you be able to delete the file, restart the computer and run a full system scan using your suite of security software, particularly Norton Antivirus, Ad-Aware, and Spybot to ensure the infection has been removed and to verify there are no other infections on the computer.

Should you be unable to delete the file through either Normal mode or Safe Mode this creates a rather significant problem, since it seems you are not able to remove the file using the usual methods. In this unlikely situation, you will need to contact me again for further advice as the steps to remove the problematic file are likely to be quite complex.