How to install USB Mass Storage Driver?

I know after Windows XP release Universal USB Storage Driver is not an issue for any USB. Two days back, I was facing USB detection issue. My Computer was not recognizing my portable hard disk either. Finally on Sunday, I got two hours to fix critical problem and share my findings with you with solution. I am share my findings based on Microsoft Windows 7 only.

"USBSTOR.sys" file is USB Mass Storage Driver for detect USB Mass Storage Device(s). You can find it in folder location "C:\Windows\System32\drivers". ‘.SYS’ files communicate with Operating System directly and guide Operating System what to do with device and how to do.

Operating System has one utility (so called, Driver Detection/New Hardware Found) for new device detection and registration for correct version of device driver to communicate with Operating System. Driver Detection utility needs INF and PNF file for device detection and registration for communication with hardware. You can find them in folder location, "C:\Windows\inf".

[Additional Information, INF file has all driver setup information and PNF file has some dependency and additional information of driver (in nontechnical words) (Technical team is Precompiled Setup Information).]

Some time USB Mass Storage Device has problems due to driver installation and un-installation frequently OR due to any possible bug of installer/setup. Installer can delete .INF, .PNF and/or .SYS file(s).

Windows 7 has almost every Device Driver backup in folder location, "C:\Windows\System32\DriverStore\FileRepository\". Go there and search folder "USBStor.inf_******" (* is driver identity number). It will have three files of USB Mass Storage Driver. Please follow instructions to restore them,

1. Copy "usbstor.inf" file and "usbstor.pnf" file, and place in location "C:\Windows\inf".

2. Copy "usbstor.sys" file and place in location "C:\Windows\System32\drivers".

3. Reboot Operating System.

4. Say AHO! After login. (Please note without AHO! USB will not work. A Joke)

5. Insert USB and use it.

Again AHO!

33 thoughts on “How to install USB Mass Storage Driver?

  1. I just wanted to thank you for this information. Couldn’t believe my eyes when my notebook installed the flash drive in no time. Aho~. Thank you so much.

  2. Thanks! This is very useful! Spent a week searching for the solution to “driver not installed” for my new USB harddrive.

  3. Can i just restart my pc??.. Cause i don’t know how to reboor..😥 Im having a prob with my pc.. I can’t install my usb because of this crc..

  4. After hrs trawling through various Win 7 forums and none offered any real solutions stumbled across this and hey presto my HDD and various Memory sticks are now working Many Thanks!🙂

  5. AHO It’s work ….🙂

    Just copy only “usbstor.inf” file and “usbstor.pnf” file, and place in location “C:\Windows\inf”.
    The “usbstor.sys” already exist.

    Many thanks.

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  7. I tried this but not function! Not AHO…
    I found the files, I have 2 yellow files repository usbstor.inf_amd64 **** and I chose one to make this, but it didn’t function, I did all correctly.
    My Windows 7 Ultimate 64bits, all pendrives function in notebook but not in desktop, my all USB entrances don’t recognize pendrives only photos camera end cellular cable.
    Please, send alternatives?? Thanks !!!

  8. Pingback: Repair Usb Mass Storage

  9. my system doesnt let me change the usbstor.sys file. it says that access denied, cuz i dun hav permission. tried the user account control settings as well. but it gives same error. need help

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