If you other PC can't even see the drive when you plug it in there isn't much we can do. I'd see if you have another USB device you can check, also plug the USB drive back in the first computer and make sure IT can still see it. If you pull the drive while it's in use it's possible to corrupt the drive. The PC would still SEE the drive, just wouldn't be able to open it. If you're computer isn't even recognizing that it's plugged in you may have a dead or disabled PC port