Cleaning it may not help. Sometimes the fan just wears out, gets slow, noisy, and eventually stops. Had that happen to a desktop system. I ignored it too long, the power supply overheated and zapped the motherboard. Suggest you do a proper fix soon as possible .... unless you want to live dangerously.

Try using the end of a vacuum hose. Suck instead of blow.

Thanks, both of you, for your suggestions. I used compressed air to blow some of the dust out, but it doesn't seem to have made much difference. This power supply was replaced not very long ago, too, so it shouldn't have gone bad already. If I prod the fan with a Q-tip, it sometimes will start up and run for a little bit, but still slowly and hesitantly. If anybody else has any ideas, please let me know. How difficult is it to replace the power supply if you are a tech ignoramus like me?

If you Google "Replace power supply on dell 5800 " plug in your own model number.

You're most likely to find instructions

Clamp the vacuum hose to the computer then fire it up whenever you use your computer. A bit noisy maybe but it would drown out other distractions.

Your fan motor either has bad windings or a bad bearing. Cleaning the fan blades won’t fix it. Gotta replace the unit.

How old is this computer?

I may have spoken too soon when I said cleaning out the dust didn't improve anything, because the fan does seem to be running more than it was before--and fairly quietly sometimes. I did go ahead and order a new power supply, though, because the improvement comes and goes! The computer is an old one, probably at least eight years old, but the power supply was replaced with a new one only a year or so ago.

audrey-

I also had a computer that was about 8 years old with a fan problem. I tend to leave my computer running 24/7. One of the fans was getting noisy and not running efficiently and the CPU was running a bit hot. Blowing the dust out made a slight improvement, but not enough. I got an identical replacement for $25 and it only took a couple of minutes to install it (4 screws and one plug-in cable). The computer was quiet again and the CPU temp dropped.

Afterwards I got to thinking about what wear a fan is subject to. My fan normally ran at about 4000 rpm, which is equivalent to about 5.8 million revolutions per day, or 2.1 billion revolutions per year. I'm amazed they last as long as they do!

There's an old trick with these fans that can help extend life, although in your case you'd need to take the fan out of the power supply. Once removed, peel back the label at the center of the fan blades and under the label is a small hole. Put a drop or two of light machine oil (like sewing machine oil) in the hole and keeping the fan horizontal, spin the fan blades to work the oil into the bearings.

It's probably not a practical solution in your case but it's a useful trick for similar fans in computers and other electronics.

Thanks, Kudzu9, for letting me know that installing the power supply isn't too difficult. I generally left my computer running all the time too, though I have been turning it off at night the last few days

I'd read about the oiling that you mention, Johnc2777, but decided it wouldn't work for me since that label must be on the bottom of the fan in this case.

My mother was the tech-savvy member of our family, but she passed away last winter. If I run into problems installing the power supply myself, I probably can get my nephew to help me. I doubt he knows as much as Mom did, but more than I do! Thanks again, everybody, for your help.

You can often find installation videos for stuff like this on YouTube. The principal rule that everyone needs to follow is to always unplug the computer before working inside it. ;-)

clean and grease

I did replace the power supply this afternoon, taking careful note of what plugged in where and snapping a couple photos before I took the old one out. At first I thought the fan on the new one wasn't working either, because it was so much more quiet, but it actually was spinning.

So far, the computer seems to be working fine. Miracles, as they say, will never cease! I did have a bit of trouble pushing the little plug things in, but apparently I just wasn't pushing hard enough.

I occasionally have problems with Windows not booting up properly after the computer has been unplugged for some reason--and that did happen this time. But that seemed to be the only problem, and it did boot up fine when I tried again. For some reason, the computer always changes the date back to 2002 during those episodes and I have to reset it. The first time that happened, I tried to access Google and was informed that Google didn't have a proper license. Perhaps it didn't back then!

Thanks again, everybody, for all your help.

There's a battery on the motherboard that keeps the BIOS powered when the machine is otherwise off so as to retain the time and system settings. Those batteries need to be changed after some years. Desktop systems typically use a disc-/coin-type battery (lithium or whatever). Some laptops have a hardwired battery that involves soldering to change it.

Secure sites (SSL) involve security certificates that have expiration dates. Validation of the certificate typically fails if the computer's time/date is years wrong.

dadoes-

Yes...I have an 8 year old all-in-one computer that is still going strong, but the battery for the BIOS crapped out about 5 years ago. I would have replaced it except you have to dismantle all the layers of internal components to get at it, and I'm not willing to do that. Fortunately, even when it's powered down or I need to restart it, it doesn't affect anything. As long as it's plugged in to the wall, there's a trickle charge that keeps the BIOS going. The only time I have to reset the date and time is when there is a power failure.

Thanks, dadoes and kudzu9, for the explanation about the date and time. I did notice a battery on the motherboard when I was replacing the power supply. It was pretty much out in the open on my computer, so I might be able to try replacing it.

audrey-

It's incredibly easy, as long as it's in the open like yours, and not buried within the innards of a laptop or all-in-one computer.