no audio, just whine from speakers

[BDrums1971]

Hi, I can usually figure out most computer problems on my own, but this one is out of my league. I downloded software for importing records/cassettes/audio into my computer. I have a synthesizer that I wanted to hook up to my computer and record some things from it into my computer. So, I hooked my keyboard up to the line in on the back of my cpu and then turned the keyboard on. I could hear the keyboard sounds coming through my speakers for approx. 5 sec., then all I got was a high pitched whine, like a mosquito. I unplugged everything and rebooted, but no change. I used headphones plugged into the line out and same thing.
One thing, when I normally turn on the synthesizer, as it is "waking up", there is a rather loud popping sound. That's normal. Could that have fried the sound card? The 5 sec. or so that I heard sound, it was not loud at all...I had the vol down on my keyboard.
1.Do I need a new sound card, and
2. Is there a problem with trying to run my synthesizer into my computer?

Any help would be extremely appreciated

[Yargwel]

Have you tried just speakers in the line out socket of the sound card - then play a sound file and see if you hear it.

Also check on the volume control applet on the PC you've not got the output muted for line in.

Oh and welcome to MG by the way.