Help regarding new mouse for my Dell laptop...

My last mouse recently got chewed up by my cousin's dog when I dog-sat for him while he was on vacation. The thanks I get... Anyways, I just received the same mouse in the mail (from China, off ebay) and it looks great. Problem is, it isn't working. The green light comes on, and when I plug the USB thingee into the USB slot, my laptop makes a noise (recognizing its existence) but that's it. The mouse isn't working. The mouse is a Logitech Cordless LX7...my previous was an optical mouse but this one apparently is the laser version. It didn't come with any software. Any thoughts?

Update: I just installed some updates from Logitech. Still not working. But my computer now recognizes new hardware: the MX600 Cordless Mouse. But that's not the correct mouse! Is this why I'm having so much trouble? Did China send me an LX7 with an MX600 USB thingee? D'oh!

---looks like other ebay sellers are selling the USB receiver, and claiming it is compatible with many models of mice...including my LX7. So...the search for some answers continues...