Windows 7 - Wireless card download speed issues.

I have a D-Link Xtreme N PCI Express Adapter DWA-556 (that's the whole product name, oh dear Zeus), and for some reason my download speeds keep fluctuating.

I've got Armstrong Cable (a local company) with DSL, and I don't really know what speeds I should be getting, but it fluctuates to this completely insane degree.

Right now I'm getting 10kbp/s download (according to the things I'm downloading), when nobody else is using our internet at all. I'm only downloading World of Warcraft (although while I've been doing that, I've been downloading a few other things every now and then - OpenOffice, Pidgin, Firefox, etc).

I've had up to 2mpb/s speeds, so it's been fluctuating from 10kpb/s to 2mbp/s. It's crazy.

I thought I'd fixed the problem when I reinstalled the drivers yesterday, but it's back again when I came back to the computer this morning.

To reference, I paid someone near me (a computer repairman professional person who did a great job on it from what I could tell) to build my setup after I'd assembled the parts, and he installed the OS as well. Everything but my graphics card seems to be working great.

The problem isn't the router, because we've had it for a while and it's a really solid router that I've never had a problem with, even when playing games on my old laptop.

Anything I can do to fix this connection issue?

Edit: To clarify on the speed thing, it's mostly at 100kpbs, and it'll sometimes go from 10kpbs to 50kpbs (it'll just go between those), or 100-150kbps. It's also gotten 700kbs-1mpbs before, as far as the fluctuations go.