Mysterious Sound Problem

[PartySized]

I don't get any sound output from certain applications.

-I don't get any Window XP OS sound prompts. The Sound Scheme doesn't give any sound output.
-I don't get any sound When playing online media that uses Adobe Flash Player.

However...
-.mp3 files, and the like, do work; I get sound output.
-Streaming video that uses Windows Media Player does give sound output.

Specs:
Windows XP Professional (SP2 installed)
200 GB Maxtor 6L200M0 HD
P4M800PRO-M Motherboard by ECS Elitegroup
Intel Pentium CPU 2.80GHz
2.79 GHz, 1.00 GB RAM

My sound card is part of my motherboard; it's a Realtek AC'97 Audio for VIA Audio COntroller. I assumed it was the problem, so I went out and installed another sound card (Diamond Multimedia XS 7.1); but despite the change, my sound problem still stayed the same. I've uninstalled the new soundcard, and I'm back to square one.

So any suggestions would be EXTREMELY helpful and appreciated.

-PartySized

[El_Roberto]

it sounds to me(pun not intended) like you need to double click the volume icon in the tray thing by the clock (forgot its name lol) and double click on that to bring up the volume properties then put the volume on them all to max and make shure that none of them have been muted.

if this doesnt fix it then i dont know what the **** it is sorry

[PartySized]

The volume control values are to the max. Sorry, I should have been more specific. I do get sound output in certain areas (.avi, .mp3, etc., iTunes). BUT, (1) I don't get sound output when playing online media that uses Adobe Flash Player, and (2) I get sound output from my Windows Sound Scheme (ex: startup sound).

[EricB]

get a new profile or try changing the windows sounds

[PartySized]

I did that, and nothing changed. The Sound Scheme is set to windows default, but I still don't hear any Windows sound prompts (ex: startup sound, shutdown sound)