at my main pc it doesn't work at my laptop it works just fine with the same cable
Thank you all for your responses.
Yes, my problem is that I cannot access to roms partition.
If I connect the SD to a Windows PC it does not recognise the drive and it asks me to format the SD.
If I connect the console and press B it does nothing (same result if I press A at the promt when I connect the USB cable to the PC)
I've installed the full img through win32diskimager and I've expanded the roms partition without problems
I'll try with another SD.
Try this try a few other data cables usb leads i was having the same problem changing to a differest lead and usb port it suddenly worked. Try that first windows normally allocates drive letters automatically i dont think anything is wrong with your sd card to be honest. And when connecting pressing button b it takes a while to connect about 30 seconds or so.
I had the same problem. Couldn't connect using my main PC, but it worked with my laptop (both Win7).
Removing drivers from unknown non-present USB devices solved my problem. I guess it was a conflicting USB driver problem (I already connected my Dingoo, GCW0 and much more in the last years).
Open a Command Prompt (cmd.exe) with Administrator rights.
This opens the Device Manager.
Enable "Show hidden devices" in the View menu.
Under "Universal Serial Bus controllers" I removed the grayed out unknown devices (right mouse button -> Uninstall).
Maybe it helps in your case as well.