Ice wrote:it's my desktop, not laptop.
If you are "comfortable" poking around in there yeah go ahead and pop the side. You will need to really pay attention to get an idea of where the noise is coming from. If it's a fan, even the CPU fan it's a pretty cheap and easy fix. If it's the HD, well that's up to what kind you want but getting your head in there and listening for a bit should help narrow it down. Shouldn't be that tough in a Desktop to isolate it really. I'm no "expert" but I've built two rigs, it's not that tough to replace most of that stuff.