I have a Nokia Lumia 1020 (909) 1 yr old. Until recently no problems connecting to pc via usb to transfer files.

Until now. My pc and every other pc I've tried says 'usb not recognised'.

I've searched online, tried all advise. Install new driver, reset phone. Downloaded update. Cleaned usb on phone. Been to Big C, they weren't any help. Can't find a solution.

Usb on phone isn't damaged. Everything else works fine.

It isn't the pc. It isn't hardware on phone. Seems to be a driver conflict.

Any informed advise very welcome.

I like working these problems so I hope you can bear with me. I would like to ask for more details.

1. USB on phone isn't damaged. What do you mean? How do you know?
2. Everything else works. Again what do you mean, what works?
3. Have you attached anything to the phone via that USB connection and it functioned correctly?
4. If #3 is yes, was it attached via the same USB cable you attempted to connect with to the PC?
5. Did you try different phone ==> PC USB cables?
6. Installed new driver -- on PC?
7. Why do you say driver conflict? I have a USB memory stick not recognized because it simply failed internally.
8. This problem on a web search showed others with the same problem. One remedy was to reboot the phone. Did you try that?
9. Another answer: Make sure your using the supplied cable. Also make sure your not using an old USB 1.X or low power USB port. I (i.e., the poster, not me) had the same issues with another cable. My [his] system had low power USB on the front of the system but high power in the rear.
10. Then added: I [he] also loaded this program and it was able to solve my [his] issues. My [his] filesystem now comes up in explorer: LINK

Here is the TROUBLE shooting link to that whole thread.

Yes I have tried all you suggest.

My pc says the device is unknown.

It say the mobile based device driver was not installed successfully.

Thks for your input.