I think the likely possibilities are faulty USB docking cable (connects for power but not for data), or the equivalent problem in the iPod side of the connection. You can try a different cable if you have one or can borrow one; that would rule out faulty cable as the cause.
Another less likely possibility is a problem with your computer's USB port. If you are using a USB hub to connect, try a direct connection to computer's USB port, and confirm that port is working properly with something else, like a USB flash drive.
If you have an Apple Store nearby, you may want to make an appointment with the store's Genius Bar (tech support staff). It would not cost anything for them to examine it, and try to connect it there (take along your USB docking cable). If it works there (and they do a Restore on it), let them know you use a Windows PC, so that your iPod is not formatted for Mac.