Line-In/Stereo Mix does not work, have correct settings and installed most recent drivers, Windows 7

I have a black macbook which I have years ago began using as a Windows computer by installing and using only Windows on the computer. It is a black macbook which I would have bought around 2007/8. I used Windows XP until now with bootcamp (mac) drivers, which worked perfectly. I often used the Line-In and Stereo Mix for recording guitar or sounds, which worked perfectly. I recently installed Windows 7, and though the playback sound works perfectly, neither the stereo mix or the line-in works. I have gone into the settings and triple checked everything, activating and checking the line-in and stereo mix settings, but it still does not work to record with. It seems to detect that I have plugged something into the Line-In socket, but when I click for example "listen to this device" or try to record, I just get a constant dull bleeping/thudding sound from the device, the volume for Line-In when the amplifier is plugged in is maxed out, even when on both the amplifier and the computer the volume can be set on 1 or very low. I have downloaded the latest Realtek drivers which always worked on XP and are meant for the macbook hardware. Unusually the built in microphone does seem to work fine.

I need these functions to make music with and to record, I can't afford pro equipment right now, so I would Really appreciate any help. Thank you for reading. Using a different computer is not an option due to my recording process.