interfearance when trying to record

[giz]

when i try to record something using software such as audacity, there is a high pitched interfearance on the recording. it only appears when i playback a recording. it is there even if there is nothing plugged into the line in or mic.
any help appreciated

 

[subprime]

Laptop? Monitors or headphones? If I connect monitors to my laptop I get interference, but not with pc. Just an idea.