Latest Wireless network driver SLOWED my Internet speed!  

I am having a confusing time trying to figure out why my internet went from 10+ Mbps down to <1 Mbps after simply downloading a wireless card driver.
From the beginning:

My wireless download speed was 10+Mbps, and I was using the Dell Wireless 1505 Draft 802.11n WLAN Mini-Card. This information is found in the Device Manager, under "Network".
The driver for the card was 5.30.x.y (I can't remember the specific version number, but I do remember it was 5.30.something.something). Upon navigating to the Dell webpage, I wanted to see if there were any drivers for the same wireless card that were more updated, to perhaps increase performance.

I navigated to the page for my computer (Dell Latitude D830), here. That page is for my model laptop. You'll notice that, in the drop down for "Operating System", there is no option to select Windows 7.

Regardless, I navigated to the driver under "Network", the Dell Wireless 1505 Draft 802.11n WLAN Mini-Card, and downloaded it. It was version 5.60.188.1, from 11/9/2009. This is where my problem began. After installing the driver and rebooting, my internet speed instantly went to below 1 Mbps. I have no clue why installing a later wireless card driver would mess up my speed.

My only hypothesis is that the driver I downloaded is only compatible with Vista. Do I just re-download driver version 5.30.x.y or something to get it back? Why did it get so slow?

How do I get my computer back to the download speed it was/should be?