|You may not have the sound enabled in the BIOS. Or you do have the newest chip and the utilities don't know what to make of it. Usually they still generate something though.|
To answer your question about Realtek. Realtek produces the physical chips. They write custom drivers for each application as required. The more features the motherboard maker wants the more detailed the drivers.
I highly doubt Realtek will be of any help to you.
Laptop HD sound is different than desktop. Generally desktop HD sound has 6 ports that are configured using the software. There are many variations of how those six ports can function. That is why the exact drivers are required. I don't think you have 6 ports for sound. Your laptop came with Vista. Microsoft has pressured vendors to NOT provide drivers for WinXP, even if they are available.
In some cases the vendors have convinced Microsoft to allow them to sell the computer with WinXP pre-installed. Those models will have drivers available. If they happen to share hardware components with another model the drivers may work even though they are intended for a different model.
Realtek is constantly designing new chips. Your laptop MAY have a chip that never had a full driver set written for WinXP. There is no easy way of determining that.
As stated Microsoft doesn't WANT WinXP on your laptop so the vendors are strongly discouraged from assisting you.
Your only chance is if your chip is shared by another model/brand that has a WinXP driver.
The issue of the sound not appearing in any snan utilities is discouraging. Are you sure you are using SIW correctly? You need to expand any heading that has promise and a + in front of it.