A problem with my wireless internet.

[leader of mortals]

I am currently on my laptop, a Dell laptop which I recently had shipped back to Dell for them to ship it back to me with a new Hard Drive. I installed the Hard Drive, and everything was great for about a day and a half. After that time, my speed seemed to shoot down to nothing.

Now, I know that wireless internet won't always be as fast as wired internet, and the closer you get to a wireless router, the faster the internet will be, but my desktop with a wired connect gets 19 mbps on speedtest.com, while this laptop, upstairs, not 50 feet from the router, gets .27 mbps. When I go downstairs, the speed shoots back up to 12 or 13 mbps. I was wondering what my problem could be, whether it's my router that's going to hell, or my wireless card that was somehow broken, or if it's any other problem.

Any help on this subject will be greatly appreciated.

Edit: I should have said that, according to speedtest, my speed is extremely unstable, going from 5 mbps yesterday to .27 when I made this post to about 3 now.