High Pitched Interference, HELP!

I am having problems with a constant high pitched noise when RECORDING from any source via line in with my sound card. The noise isn't present whilst just listening to sources through the sound card, but when i record the sources in sound forge and then play them back, the constant high pitched noise is there on the sound file. I didn't have this problem with the sound card built in to the motherboard but when i upgraded to a PCI sound card the problem started. It is wierd because the noise is only evident once the file has been recorded, otherwise there is no high pitched noise. I was going to move the card down a few slots, but i haven't really had time. Would this help? Please post any suggestions on how to solve this annoyance. Thanx in advance.

It might help. What else might help:

* Take all the flourescent lights in the room, throw them in the trash. Replace with incandescent lighting. Your eyes will thank you too, as will the electric company (*sigh*)

* Take all cables which are audio and all cables which are power and ensure that:
- a. they are as far apart as possible
- b. they never, ever, ever cross
(This will cause a 60 cycle hum (low), in most cases, not a high pitch.)

* Turn off any television or similar devices. Just for the heck of it (and for good reason) turn off your CRT display too, while recording, and see if the sound goes away. If it does then: >> move the CRT.

Anything with a tube or a motor is suspect, including the fans within the case.

Sounds like, no pun intended, that you may be picking up interference. Here are some more things to check:

• 
  Check AC grounding and make sure you are using a three prong plug.

• 
  Verify that the computer case is grounded.

• 
  Check and insure the flat, threaded nut that secures the 'lin-in' jack to the card is tight.

• 
  If you are only using one input cable for 'line-in', test the cable and make sure that left, right and neutral are balanced and securely connected at both ends.

• 
  If you have a lot of spurious energy around, other electronic equipment, etc., consider using a shielded input cable.

• 
  Check the sound card's shielding and make sure nothing is loose or disconnected from the board.

Good Luck