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I have several unknown devices within the Device Manager. These appear to be devices that install their own programs and services to operate, however I have no use for them.

Does leaving these devices in an unknown state slow down my computer at all, or would I be better off installing their drivers and leaving their program entries in Add/Remove Programs?

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It might be helpfull for your question if you identified the devices you where thinking about removing. – James Jenkins Apr 23 '13 at 16:44
up vote 4 down vote accepted

unknown devices means there is hardware of some sort that does not have the proper drivers installed. This does not mean there will be performance impact, as an external hard drive that is not recognized is simply not recognized. The OS is not constantly trying to figure it out, it tries, sees nothing and gives up.

That is not to say there is not any impact ever.

Windows may try at different times to update the devices, say on a reboot or another install. Introducing short delays while it queries and verifies it does not have the right driver.

Also, since you don't state what hardware this actually is, or in a more general case there are times when there is a huge performance impact. If Windows sees a video card as an unknown device for example you will feel laggy and see all sorts of issues related to performance.

If you are not using whatever devices, then I would remove them. Yellow and red in the device manager is a big no-no in my professional opinion. Otherwise find the drivers.

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It doesn't slow down your computer as there are no processes or CPU activity associated with them. It adds clutter to Device manager and in general I would say that you should either remove them or fix them. But it won't have an impact on performance.

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Probably never is too general and potentially inaccurate... shouldn't or rarely seems appropriate. – AthomSfere Apr 23 '13 at 16:47

You never really know. It's like driving a car that has a warning light that says something is wrong or missing. It could be your spare tire is not there or it might be one of your tires is low or even worse the wheel has a lug nut missing. Only one of these is potentially dangerous and should slow you down. One is a nuisance and the other is downright dangerous.

There are several on-line service providers - some quite reputable - that provide a scanning utility that will tell you if it is important, if it can be fixed and then will fix it for you. Most of these services will charge for the repair not for the scan. Most want repeat business so they will charge you monthly or yearly.

One thing is certain no computer builder builds equipment with devices that are normally not used. So check with the manufacturer's site and ask their tech people before spending money on something you might not be using or needing. I have a Toshiba laptop that uses a chip that provides usb bus access for software driver emulations of a modem, a cd-rom drive, sd card services, etc. The service I use found that my modem (which I don't normally use) was an unknown device when I upgraded my OS to 64 bit from 32 bit. I would not have found it because I didn't use it. Thanks to them I now have a functioning modem the absence or presence of which does not speed up or slow down my system , it only enhances it's usefulness.

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We have seen, especially with XP, less with W7, that installed devices, not the ones with drivers that come built into W7, the ones you have to use Windows Update or download from the manufacturer web site, that when not present can slow apps down, in particular, apps that use those devices, like a printer for instance with Word.

Even if the main app isn't open, if a job is queued for a printer, the spooler will be looking for the printer. The spooler or other jobs like the ink-supply monitor may be looking for it too.

Similarly, if you have an MFD (multi function device), such as a printer/scanner, any manufacturer's app to support scanning may be looking for the device. HP's scan software is really bad with this. We find that Windows scan works as well. HP might get you OCR and other image manipulation SW but I avoid that if at all possible. Use the most minimum driver you can find.

If your external HDD is used to shadow the main drive and if the external drive isn't there, something may still be looking for it to be connected. Maybe not constantly, but consistantly.

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