Today I re-formated my PC and all was well until I had a random shut off. Thinking it's because I had a lot of dust inside of my PC I brought a can of condensed air and sprayed the inside of my pc. After waiting a hour or so I put back on the shield and when I logged on my pc, my pc said the CPU fan is not being detected and I had a random shut off again. How do I fix this problem?

Shut down pc.
Open the case.
Boot up with the tower open on one side.
See if the cpu fan spins up.
After a good clean it's natural a fan gets stuck and needs a little help getting started again.
How you go about doing that is up to you. Just be careful. As a rule of thumb, you should not come into contact with any parts inside the case, while its on.

See if that is your problem.

The fan is working it's just not be detected. I tried again but the same thing happened except it didn't shut up. I'm pretty positive if I left it on it would of shut off though.

That message you get. Does it say anything more that that. If it does, would you write it down and post the full error.
If the fan is spinning. It sounds healthy and the system does not shut down unexpected. That would be a good sign. Obviously.
You could try enter BIOS (del? at bootup). You might find some temperature readings and fan speeds there. Look around.
If it's a sensor that is not detected, that shouldn't be to important.
You didn't take anything apart inside the case, when you cleaned it up.

Not sure what else to do about it at present.

It says: "Alert: CPU fan not detected".

Then it gives me options to go to utilites, continue, etc.

I would keep an eye on that fan for a while. Keep running the system with the case open.
If the system remains stabil, I don't see the problem, if not, then you know where to start.
Here's an excample of that error from Dell

http://support.dell.com/support/edocs/syst...it/x9719c20.htm

I don't think you should worry. Like I said, it might need a little time to recover from the clean.

That's just my personnal opinion and I'm not a technician.

Hope that's some conselation to you.

The fan doesn't need time to recover from being cleaned, it is either going to work or not work. Have you checked to be sure that the connector is properly seated?

Yes but nothing has been unplugged. This is the first time it has done this. When I had my pc running earlier, this was not a problem.

That's not always true dc3.
We do not all possess brand new fans and when a fan get's really dirty, you gonna blow stuff all around when you try clean. That stuff is gonna stick.
I had fans I had to push using a screwdriver just to get started and it took days for them to gain proper momentum.
One of those is the fan on this very CPU.

In that case the fan is failing. Maybe not right now, but it will fail
Mark

That might be so, but until it does it still needs to develop momentum. All fans will eventually.
On the subject will then agree to disagree, because I have plenty of living prooph, you are wrong my friend.
It's just dust that needs to get out. Nothing sinister about it.

over and out.

meh... it's a fan... buy a fan... they're not exactly expensive.

Did you try unconnecting the fan...and then reconnecting it? With the power off, of course.

I've not seen that message but I would certainly have a backup fan/heatsink available.

Anything man-made can go bad...at any time.

Louis