worst noise ever

ok i dunno what the hell this is but when i turn on my comp all of the sudden it makes this high pitched ringing noise like one u hear when u listen to music too loud. IT wont stop!!! i turn off the comp
then on again and there it goes. The last thing i did was install 3d mark and when i do benchmarks the noise stops

Not sure what it is, but it may be a sticky fan. To fix this, carefully pull the stickers off your fans and even more carefully add a drop of oil. Rotate the fan blades around for a bit by hand, wipe any exess oil off, and then carefully place the sticker back on. Make sure your fans are not attatched when you do this, you do not want to get oil on your hs because it will reduce its cooling capacity.

I'm almost positive it's the monitor. You're probably running an older monitor at, or near, it's max resolution and frequency. The same thing happens on mine. When it boots up, it's at 800x600x60, so is nice and quiet, but when windows starts it goes to 1024x768x60 (it's max setting). When this happens, it makes that ringing sound. I suggest you try a different monitor or different settings and see if that does it.

XP 2500+ Barton @ 2241Mhz
A7N8X Dlx
2x512MB Corsair PC3200
MSI GF3Ti 500
16x DVD-ROM
2x80GB 7200RPM Maxtor
Onboard audio

My monitor is an 8-year old POS. I'm surprised it still turns on. I'm going to be getting an LG or Viewsonic Flatscreen display, but I also need a new desk to hold it. Gonna be a couple months before that happens

XP 2500+ Barton @ 2256Mhz
A7N8X Dlx
2x512MB Corsair PC3200
MSI GF3Ti 500 @ 265/570
16x DVD-ROM
2x80GB 7200RPM Maxtor
Onboard audio
3DMark 2001 SE - 10528