Realtek HD Audio clips input signal at half max level

Hello all,
the Realtek HD audio on my Hp desktop, win7 64bit Pro, has never handled input signals properly, any line in or Mic in signal gets clipped at half level. So if I want to record input - I usually use Goldwave or Total recorder - then the output file is clipped at half max.
I've attached a screenshot - I recorded a pure sine wave 400Hz line-in input from a signal generator using Goldwave, and you can see what's happened to it. It doesn't look like a pure sine wave any more, and it doesn't sound like it either.
I could have recorded the same signal with Total Recorder, then displayed the output file in Goldwave, it would have looked the same - so I assume it's the Realtek audio that's doing the clipping, before the signal ever gets to the recording software.

I tried a driver update - R 2.82 Device Manager: 6.0.1.8186, hasn't made any difference.The only sound I can input that doesn't have this problem is the USB mic from my external webcam. That leads me to think that I could get line in to record properly by using an external USB line in device, but I'd still like to know what's going on with Realtek.

Thanks, PosslPussl

I'd have to sit in front of your PC to see what is really going on, but on the surface it looks like a driver or another software is messing around. To rule that out you want to get rid of EVERYTHING sound related and start over. Or, try booting Hiren's Boot CD and see if audio is still clipping. If not, the issue is your current OS environment with software or drivers. I'm almost certain this is driver or software that's doing it. Without being there your guess is as good as mine.

That almost looks digital and not very sinuous. There is no use of virtual audio cables or something like that?

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Are you using onboard or dedicated for sound? If dedicated, go into BIOS and make sure the CODEC or onboard audio is off.

Also, there are generally two front panel header connectors for audio. One connector will be labeled "HD". You want to use that one plugged into the sound card's header connection.