Wireless Connectivity

I have been using dial up for the longest but decided to utilize local hot spots for High Speed internet. I purchased a Belkin wireless G+MIMO USB adapter. For a couple of weeks I experienced very high internet speeds. Then suddenly my internet moved very slow. My computer still read that I had connection speeds of 12 MPBS but when I checked my download speed and upload speed on a website I was only getting 20 kpbs for both! When I tried to dial back up, I would get normal dial up speeds of about 46 Kbps. I called Microsoft and they told me my adapter was damaged so I purchased a very expensive Netgear Wireless N USB adapter. To my surprise I am having the same problem. The computer says I have speeds of 24 Mbps but the internet moves slow and when I check the speeds Im really only getting a 27 kbps download and a 400 kpbs upload. What could I do Ive tried adjusting almost EVERY setting. The dial up still runs at its normal speed but the wireless will not. Ive tried using firefox thinking it was a problem with internet explorer and that didn’t work. Ive tried seeing if there were some program I had that was using up all the bandwith and there were none. Ive tried almost everything that I know of, If anyone could help it would be greatly appreciated as I have grown accustomed to high speed internet and suffer when I have to use my dial up. I use windows to configure my wireless connection