Fan test are simple : when the PC is active (but hardly doing anything!) simply block the fan you suspect is making the noise for a second. if the noise stops immediately, you have the fan in need of replacement.
Turn the PC off an look how this fan is oriented and wired up (take photos if need be) and unscrew it from it's location, take the fan to a store where you can buy PC parts and ask them to get a similar one (exactly!). Put the replacement fan back (now the photos you took earlier could be of help) and activate your PC to verify it works without noise. When it does, close the case again , turn the PC back on again and pat yourself on the back for the repair job you have completed.
Computers do attract a lot of dust, so it might be a good idea to remove the dust from fans and computer parts.
It could be that the fan inside your power supply is making the noise. If the back of your power supply consist of evenly spaced holes, chances are that you have a model that has the fan on the bottom of the power supply. Get a professional to check and/or replace this fan...or spring for a new power supply. This model is usually more expensive (but worth the money!)
However, if you have a power supply that has a set of holes forming a circle on the back, than you have a model with the fan on the back. When the power supply is active, press on the metal in the center of this circle. If the noise changed or went away, it is likely this fan is giving problems. If you want to replace the fan, get a professional to do this. Usually it is easier to get a replacement as they are relatively cheap (even here in Paraguay this model (500W) costs around 10 USD).
In any case, always check/remember how all connectors are connected before you disconnect any of them. That makes it easier when reconnecting. Well, it isn't hard and most connectors are shaped in such a manner that they fit in one way only, without the use of force. Still, if you are unsure, photos can be of help.
As a general rule, if you want to use force to disconnect/reconnect anything inside a PC, you are doing it wrong!
Cloning a hard disk (bit-for-bit copy) to a different hard disk isn't difficult, but requires attention to detail. First, write down all info (brand, model, serial) of each drive you plan to use for cloning (pen and paper). Identify which is the Source hard disk and make sure you know the info of this drive by heart. The other drive will automatically be the Destination.
Doing a bit-for-bit copy means that any data that exists on the Destination will be overwritten, so back this up first, if you want to keep it!
There exist a lot of software (free/commercial) to clone a hard disk. I'm personally fond of 'Miramay HDClone', 'MiniTool Partition Wizard' and 'Eassos Partition Guru'...in that order. HDClone lets you boot from CD or pendrive, select the Source and Destination and start the cloning. Depending on the size & speeds of the hard disks and the version of HDClone you use (the free one is the slowest) this can take time. Please use the available SATA connectors on your motherboard to connect the hard disks, any other way diminishes the chance of creating a successful clone significantly.
Don't expect free software to be able to clone a bigger Source to a smaller Destination, for example a 2TByte Source (bigger) to a 1.5TByte Destination (smaller). The Source and Destination must at least be the same size or the Destination has to be bigger.
When this operation is finished, turn the PC off (completely), disconnect the Source hard disk (completely) and start your PC again. If the system boots and everything is working like you expect, it is safe to assume the cloning operation was a success. Turn off the PC again, remove the Source and keep it in a safe & dry place, preferably in an anti-static bag. This way you still have a fall-back if after a month of using the clone you are not satisfied with the clone. To be really complete, mark the Source with a label stating its purpose and why + when you took it out as a reference. Just make sure you don't cover any hole on the hard disk.
Hmm, thanks Shades for the effort, forgive the choppy editing as I try to parse the items.
"fan you suspect" ... Unlike the old days, and tell me if you think there's a latent bug, but SpeedFan is giving me about five fans doing various things ... (stream of consciousness, noise went away entirely for 30 seconds.)
So I'd be fine if it was one fan and you set it like 950 rpm or whatever, I think I did that once a decade ago on an ancient machine... but Speedfan is confusing me so I really don't wanna mess with stuff that gets VERY rapidly over my head!
(Post in Progress) - (I think in layers)
I removed a little dust from the top cover. About all I can do. I'm SO not a hardware guy so any suggestion of "open the casing" won't work for me!!"
(Another x-second lull of nothing. But the CPU wasn't tasked, it wasn't doing anything anyway.)
"chances are that you have a model that has the fan on the bottom of the power supply"
I have no idea what this means. There is no model. A buddy of mine built it from scratch with parts from the ground up and I vaguely even recall him explaining the heat reducing paste. I haven't been inside the case since and I don't plan to. I'm basically too much of a hazard.
(Back to a lull) No HD would fail that wildly. (Would it?!) I'm thinking fan. I just don't know much yet.
We get a little more my style here:
"Cloning a hard disk (bit-for-bit copy) to a different hard disk isn't difficult, but requires attention to detail. First, write down all info (brand, model, serial) of each drive you plan to use for cloning (pen and paper). Identify which is the Source hard disk and make sure you know the info of this drive by heart. The other drive will automatically be the Destination.
Doing a bit-for-bit copy means that any data that exists on the Destination will be overwritten, so back this up first, if you want to keep it!"
A. No pencil and paper write-downs. Tools!
B. Source and Destination are a snap ... there are only two drives!
C. Info by heart ... this one is a fair point, and it would take a little bit of care copying to merge my (older) backup with new stuff, along with a read of Programs Installed.
Then "OverWritten" is fine. ... because "We built this system ... we built this system to ..." ... uh ... have a spare drive 8 years later when the primary fails? But I'm still thinking fan. I'm trying to listen to the HD under the fan.
As to your last points, the source and destination are (supposed to be) twin drives - same size and specs. So cloning should be easy.
But ... I have grown both wary and weary of people claiming things are "easy". Put bluntly, they innocently/maliciously "forget" stuff that makes total life harder. So ... stuff. I'll stop this post here.