You're connected wirelessly to your router, I suspect. The speed that you're showing in Windows at 54Mbps is the speed at which your computer communicates with your router and other computers within your network. You internet connection speed is independent of that and depends on several factors:
1.) The speed that you're paying for
2.) Internet traffic overall
3.) The upload speed of the person you're downloading from.
4.) Network cabling quality and any small rodents that may have nibbled on them.
5.) Quantity of Gremlins