Odd noise when turning on computer

I recently noticed this squeaking like noise that sort of sounds like a slipping alternator belt as soon as I turn on my computer... I'm worried it might be my hard drives but it's hard to pinpoint for sure. Can fans sometimes make this noise? The noise doesn't last very long, maybe a second at most, but I'm still a bit concerned.

Pull the cover off and see if you can tell where it is coming from. If it is still difficult to tell, you might want to unplug suspicious components one by one.

--pak

my nb fan did that on 1 of my mb's once replaced the nb fan issue went away

most likely its the bearings on one of your fans.

my hdd squeaks like bad brakes when it comes to a complete stop when i shut off my comp...

i want to open 'er up and spray wd-40 on the bearings of the motor