Either you didn't create the USB W7 from a good ISO image, where exactly did you get it from? Or you didn't remember to change the Boot Preference Order in your Thinkpad's BIOS. This can usually be changed with <f9> or <f10> key on startup; download your Users Manual from Lenovo website for exactly which key. You can also try this with your USB drive on a different working computer that has any version of windows on it. If that other computer won't boot your USB drive, you probably didn't make it correctly, or have a corrupt ISO image file. Microsoft has scrubbed the Internet clean of most of those W7 ISO images, so a good one can be hard to find. Try using this link: Link Removed
Using a link to an actual...