Hard disk not detected

Hello,

I downloaded a software called: serial number changer. and I changed the serial number of my removable hard drive. I lost the new serial number. and now my laptop is not detecting the removable hard drive when i plugged it in the laptop. I tried to plug the drive in another laptop, but also it is not detected. the OS running on my laptop is vista. I don't want to format the drive. Please help !!