I can't tell how you set this up or what hardware is in play. It's up to you to tell all that.
But a common speed loss is when folk don't follow this forums top posts with the suggested settings. PLEASE don't take offense. I type all my replies and rely on the top or sticky post.
I have a basement home office with a Dell Studio desktop with Windows 7,64 bit. Speed was fantastic. I purchased a Dell Studio laptop with the same operating system as the desktop and wanted to create a home office network.
My ISP is a cable company and the cable access point is in the basement, initially to a cordless telephone with the desktop PC a few feet away and TV service provided to the upper two floors in the house.
To set up the network, I purchased a Belkin Play router. With Belkin support I now have a network with the desktop wired and the laptop wireless. However, I paid a price in that my desktop speed is probably half of what it used to be and frequently I cannot connect to certain web sites on the first attempt.
My specific question is, do you think the proximity of the cordless telephone is the cause of my problems and if not any suggestions?