How-To Geek

Ask HTG: Diagnosing a Flickering Monitor, Skipping Duplicate Files, and Editing the Hosts File


Once a week we round up some of the reader questions we’ve answered over the previous week and share them with the greater readership. This week we’re looking at diagnosing flickering monitors, skipping duplicate files while copying, and editing the Hosts file to get rid of annoying software reminders.

Why Is My Monitor Flickering?


Dear How-To Geek,

My computer monitor has started flickering. I’m not sure if it started flickering when I switched to CFL bulbs in my office but that’s the only major change I can think of. Where can I start diagnosing this annoying flicker?

Flickering in Fresno

Dear Flickering,

There are a couple different things you’ll want to look at in order to diagnose. First, if you have an older CRT monitor there are quite a few factors you’ll want to look at. The easiest thing to check is the light bulbs. Remove observe the monitor with the new CFL bulbs off. If there is no flicker without the bulbs then it’s likely you’re computer monitor’s refresh rate is set at or around 60Hz. Fluorescent bulbs, thanks to the 60hz US electric lines operate at, will often flicker, however minutely, at 60hz. If you’re using fluorescent bulbs with a CRT monitor it’s quite possible the flickering of the bulb and the flickering of the monitor’s refresh are working together, as it were. You can either switch to incandescent bulbs (which don’t suffer from electrical flicker) or adjust your monitor’s refresh rate to a higher setting.

If you have an LCD monitor there is no refresh flicker as LCD monitors refresh on a pixel-by-pixel basis and not with the sweep of an electron gun (as CRT monitors do). Again, turn the new light bulbs off and observe the monitor. If the monitor is flickering there are two probable causes. One, you’ve got a bad power supply to the monitor and and it’s causing the CFL bulbs behind the LCD panel to flicker slightly. Two, the power supply is fine but the bulbs are going bad—fluorescent bulbs are notorious for flickering at the end of their life cycle.

Finally if you’ve tested things with the lights off and found no flicker, it’s possible there is nothing wrong with the monitor at all but the issue is entirely with the CFL bulbs. Not everyone is sensitive to the 60hz flicker of fluorescent bulbs but those that are find it nearly impossible to ignore. If you’d like to stick with energy efficient bulbs we’d suggest trying out a different brand. Some brands run at a higher voltage/frequency and the flicker will be less noticeable or gone altogether. Alternatively you could try out LED bulbs which, though currently more expensive, are flicker free.

How can I Copy Files While Skipping Existing Matches?


Dear How-To Geek,

I’d like to easily copy files between directories on my Windows machine but with more features than the default file copier offers. The biggest feature I’d like is the ability to automatically skip duplicate files (to not overwrite files in the receiving directory). What would you suggest?


Copying in Colorado

Dear Copying,

Although the default file copier in Windows has improved a lot over the years, it is still quite bare when it comes to features. We’d suggest checking out previously reviewed SuperCopier to meet your upgraded copying needs. Not only can you set it to automatically skip existing files in the new directory but you can specify other collision settings like renaming the old or new files. SuperCopier also has a host of other great features including the ability to reshuffle the copy queue (if you need a file that’s at the end of the queue to to copy sooner, for example, you can bump it up to the top).

How Can I Edit the Hosts File?

Dear How-To Geek,

I have this program on my computer that constantly phones home and had this annoying reminder system. I called the company to ask if I could disable it and they said there was no toggle in the actual application that could turn the phone-home feature off but that if it really bothered me I could edit the hosts file. The tech support guy essentially said that editing the host file to the company’s update server address to would kill the annoying reminder system. The only problem is that I have no idea what a hosts file is and how to edit it. I’m running Windows 7.


Hosts Confused in Houston

Dear Hosts Confused,

We’re impressed you found a tech support person helpful and open enough to give you useful advice like editing the hosts file to get rid of annoying reminder. The hosts file is a hold over from the early days of the internet and pre-dates the use of centralized DNS servers. Essentially the hosts file is a text document on a computer that helps resolve addresses at the local level instead of at the remote DNS server. You can use the hosts file to override DNS requests. You could, as an example, prank your friends by using the hosts file to redirect to Check out our guide to editing the hosts file here. What you’ll need to do is create an entry in your hosts file that points the address the tech support guy gave you (i.e. to so that when the program goes to call home it just bounces the request off the local computer.

Have a pressing tech question? Shoot us an email at and we’ll do our best to answer it.

Jason Fitzpatrick is a warranty-voiding DIYer who spends his days cracking opening cases and wrestling with code so you don't have to. If it can be modded, optimized, repurposed, or torn apart for fun he's interested (and probably already at the workbench taking it apart). You can follow him on if you'd like.

  • Published 12/19/11

Comments (8)

  1. Steve

    One time I had speakers near a CRT and the magnetic field from the speakers made the monitor flicker…

  2. Merlin

    @Steve: That’s correct. Because the speakers have magnetic fields. They have magnets that are combined with electromagnets which in turn are connected to the speaker membrane to produce sound.
    These magnetic fields influence the beam bending magnetic fields in the CRT and thus create an interference which makes the image distort or flicker.
    If the speakers are well shielded, this influencing will be minor to nihil. But most speakers do not have that kind of shielding.

  3. GeorgiaCowboy

    I had the speaker problem also, BUT it was only with the “powered woofer”. It needs to be kept at least a couple of feet from a CRT monitor.
    Some people don’t know that woofers are “omnidirectional” meaning to sound appears to come from all directions. You can place it most anywhere. I have mine mounted under my desk for space reasons. Works great and is out of the way.

  4. dima

    I just want to add a note about copying with automatic skip. There’s this wonderful command built into Windows 7: robocopy. It’s very powerful and has a lot of advanced options. I use it in a batch file for scheduled backups. You can set it to automatically skip existing files and even remove files that don’t exist in a source directory which is perfect for backup/mirroring.

  5. DBigWoo

    Actually, incandescent bulbs flicker at 60 Hz too. Technically, that is. Since the current going to them is alternating (AC), they are receiving pulses of voltage. The reason that an incandescent light bulb appears not to flicker is that the light comes from a glowing element in the bulb. The element heats up very quickly, hence, when you turn on a light, it pops on full blast immediately. As the power drops in the cycle, the element starts to cool. But it takes longer to cool off than that short time that it is without power. So, before it gets a chance to stop glowing, it is juiced up again and back to full glow. Rinse and repeat as needed.

    Another issue that I found with the new CFL bulbs is if you have them plugged into a circuit that has some type of electronic controller. Most people are aware of the dimmer problem. With that, you just have to remember to look for dimmers that are CFL friendly and CFLs that are dimmer friendly. The issue I found was with a ceiling fan. Since it was an old circuit, I opted to use the ‘remote in the wall’ option with a receiver in the fan housing. It worked well until I got eco-friendly and put in CFLs. As soon as I did, I noticed a flicker in the room. More of a pulsing, really. Since I had just installed the CFLs it was easy to determine the source. Had someone else done that, it would not have been as easy as everything – including the screen – seemed to pulse.

    The fix for the flicker from the CFLs on the remote controlled circuit turned out to be easy. I just replaced one of the three with an incandescent bulb and all is fine.

  6. antonyananth

    t h x sir

  7. gilteon

    @DBigWoo: Actually you could say that the incandescant bulbs are flickering at 120Hz since they will dim both times the sine wave crosses zero. CFL’s probably do so as well.

  8. alkolkin

    I have to say, this version of SuperCopier is absolutely terrifically fast! I never paid attention to this product you reviewed because who needs it? Everyone, that is who.
    What I never understood is that it REPLACES the Windows Copy command (I use Windows 7 x64 w/ an SSD for the OS) and it is like WOW fast.


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