Can't install Realtek Driver(s)

Hi, I have a HP xw6200 with Windows XP SP2 installed. I am not very bright with all this driver stuff and am not really sure what all the specs that it says my computer has are. Though this is what it says in system:
Computer:
Intel(R)
Xeon(TM) CPU 3.20GHz
3.20 GHz, 3.25 GB of RAM

I play games quite a bit and I enjoy using the programme Fraps to record them in HD. The problem is that to record my voice aswell as the games sounds I need to have Stereo Mix in the recording section of my volume control. All the videos that I have seen on how to obtain this say to get Realteks Audio Driver(s). I have downloaded the .exe and .zip files for the XP version and it appears to install fine with no errors though when I reset my computer like it asks me too, there is nothing to do with Realtek in my control panel and the Stero Mix option is not in the volume contols. Sorry if the info I am giving is like white noise and not relevant. Im just a bit clueless about all this stuff. I am almost definate I have left some info out which you probably need so I will be patient and wait for someone to help out.

Thanks in advance ^_^