Advice/Help please!

[twistedfaith]

Over the last few months I've been having an intermittent problem with my computer. When I am in windows, the computer will suddenly grind to a halt and programs etc will either freeze up, or take ages to load if I have tried to open one. At this point the soundcard emits a hissing noise, like static on a TV - then it stops, after this point all I get is hissing if I try to play sounds, videos etc and my computer still runs really slowly.

If I try and restart or turn off the computer using the "proper" method (ie, start menu, shutdown/restart) windows closes, the monitor switches off - but my computer remains on and doesn't shut down at all no matter how long I leave it. At this point all I can do is turn it off. There have been a couple of ocassions where the computer has refused to go through POST after this has happened, sticking on detecting CD and Hard drives.

It doesn't seem to happen at any particular point either, sometimes it happens as windows starts, sometimes it happens when its left idle or when I'm playing WoW, music, videos etc. For the most part it has been an annoyance, but now its getting more frequent. What I was wondering is, would putting in a PCI soundcard help or is (as I suspect) the motherboard on its way out?

Sorry for the wall of text, and thanks in advance to anyone who answers. My computer spec is as follows:

Windows Vista64 Home Premium
Asus P5KC Mobo with onboard HD Realtek soundcard
4gb Corsair DDR2 6400 RAM
Intel Quad Core Q6600 Processer (running at stock speed)
Nvidia Geforce 8800 GTX

 

[twistedfaith]

No, its actually built into the motherboard, its not removable in any way. The only way I can "get rid" of it is to disable it in the bios.

 

[twistedfaith]

I have an update for this problem, in the last 20 mins or so my computer has repeated the problem I have mentioned above earlier this month. I left the computer to its own devices whilst the problem was ocurring, came back and found that my system has calmed down, no hissing etc and seems to be running at normal speed. However, on opening My Computer I have found that my secondary DVD drive has disappeared, I restarted my computer and it gets stuck on the POST (Which I have also mentioned above) but this time I left it for about 10 mins and it came back with "No device found on SATA 4", it then booted into windows normally, but still with no secondary drive. I have also noticed that my soundcard shares the same IRQ as my secondary SATA controller, I dunno if its relevant, but I'm going to unplug the DVD drive and see what happens...