High pitched humming sound...

Hey guys, i'm new here and wanted to run a question by you to see if i can get some help. I have an ABS copmuter (from newegg), pentium 4, mostly new stuff that is a year old. in the last month or so, whenever i turn it on there is a really loud, obnoxious, high pitched humming noise coming from somewhere inside the computer. its hard to tell what its from, but i dont think its the fan in the back of the computer. this had happened a few times in the past, but usually after a few hours of being on and having numerous applications open at once (music, internet, word, etc). any ideas on what to check out or what to look for?

my guess would be something is obviously failing in there but i dont know what...

thanks in advance!!!

 

mabye somethings hitting the cpu fan. it happened to me once

 

Have you cleaned out the insides?!? Could be crud build up and the CPU fan is stressed as you imply it occurs underload so maybe you need to do a spring clean.