Strange Sound Problem

I'm not exactly sure where to post this problem or even how to search
for this problem. If anyone knows a better place to post or a way to
search for answers to this problem please let me know.

Computer information:

Windows ME
Compaq Presario
256 Mb RAM
Nvidia GeDorce2 MX graphics card
Sound Blaster PCI 128 Audio card

All this came with the original purchase of the computer. A 52x CD-Rom
Burner was added - a generic brand.

The problem is occurring with the sound on the computer. Sound was
working until an SVCD MPEG file was played. Now, sound will only play
when Compaq WinDVD is open and playing any mpeg file. Once that has
happen then the sound functions normally but if that isn't happening or
the program is closed then the sound is no longer available. That
means all sounds even system sounds.

Actions taken so far:

Run spyblocker, adaware, spybot, Norton System Works (Antivirus, Disk
Doctor, etc), WinDoctor, Scandoctor and deleted the files that were
thought to have been causing the problems.

I am really at a loss as to why this is happening and I don't even know
how to begin troubleshooting the problem. Any help would be
appreciated. This is not my computer. It is my brother-in-law's
computer. Please let me know if you need any more information.

Thanks in advance,
Andy