I got a brand-new 2TB Passport, plugged it into my old ('10, Win 7 64bit, USB 2.0) Toshiba laptop, and loaded up all my files. There were no problems at all. Then I plugged it into my new (USB 3.0 but still Win 7 64bit) Asus laptop, and tried to open a file. Every ten seconds or so, the drive stops being recognized/shown, and then it comes back, then goes away, then comes back.
Both times I’ve been using the USB cable that came in the brand-new box. Same OS, same cable, same drive, but on this laptop it won’t stay readable more than 10 seconds at a time. I’ve tried different USB ports to no avail.