|"750w corsair whatever the main the one is"|
Is that the power supply?
If it is, that's got more than enough capacity, but it has a load on it of about 87%, or possibly more.
"2x 4870's CF"
Minimum Power Requirement (for the system's PS) - 650 Watts
"amd phenom II 955 BE" - 125 watts
PSs CAN produce noise, but that's quite rare.
Do you have another PS, or can you borrow another PS, you can try? (650 watts minimum capacity for two 4870's; ~ 550 watts for one)
Are you using the onboard sound, or a sound card in a slot, or some other additional sound adapter connected to the computer?
You can use a sound adapter (e.g. a USB connected one) that is designed to bypass using the onboard sound, but I don't know whether it would pick up the high pitched sound or not.
If you're using a sound card in a slot, try installing it as far away as you can from other cards inside the case, or try removing it.
Is the high pitched sound only there after Windows has started to load while booting?
If yes, it's probably coming from, or because of, the video card(s), either because of the card itself, or because of the load it's placing on the power supply. In that case, if you have two cards, try installing one card at a time.
(I have worked on one dual boot system that generates a faint high pitched noise in XP but not in Vista - it seems to come from the video card itself - Visiontec HD AIW - Radeon 3650 - can't hear in the onboard sound output - it probably doesn't show up in recordings unless a mic is is used close to the computer).
Have you tried recording anything with other than a microphone close to the computer to see if the high pitched sound is picked up in the recording?
A computer can pick up sounds from it' s environment.
Don't use an audio cable from a CD or DVD drive connected to the sound adapter inside the case - you don't need it with modern drives - all sound can be produced via the data cable.
Route data cables as far as you can away from fans and the cards in the case.
Close up the case - the metal blocks a lot of stuff that would otherwise be picked up, or reduces it' s intensity.
Keep cables connected to the computer as far away as you can from anything that might generate sounds it can pick up.
- unshielded speakers (most ones for computers are shielded; most others are not)
- fluorescent or halogen lights (their ballast or transformer)
- power adapter cords, their transformers
- AC cords
- the cable that connects you to the internet - coax or telephone.
- if it's a coax cable, it might have an iffy connector on the end of a cable, or a loose connection, or be connected to an iffy cable splitter, somewhere.
- if it's connected by a telephone cable, the cheap flat unshielded cables most people use act like an antenna - noise can be picked up from any phone cord connected to the same phone line that has the DSL or ADSL capability in the place you have the computer - you may get noise from other devices connected to the same phone line - all non-DSL or ADSL devices on the same phone line should have a DSL or ADSL filter between them and the wall jack.