I recently removed my hard drive from my old computer. I bought a hard drive enclosure and put my old hard drive in it. My external drive connects through a USB cable. When I connected my external drive to my computer, it detected it and said that was installed and ready to use. However when I checked on "My Computer" it wasn't there. Apparently it wasn't assigned a drive letter. And for some strange reason now when I connect it to my computer, it starts lagging like hell. And it still is not assigned a drive letter. This is my first time using an external drive. I dunno if I made a mistake in something. All I know is that I need help.