To start off, your router supports only "B" standard so the maximum throughput of your wireless card in the laptop, and all other laptops using the wireless router will be 11 mbps, as opposed to 600 mbps (max. of wireless-n) However, you should still be able to get decent downloading speeds with that, assuming there is only one user on the router... If there are multiple people using the router, 11 mbps would not go very far.. Say 3 people wanted to use the wireless router, then each of you would be limited to approx. 3.6 mbps. On top of that, the /b standard uses csma/ca, a protocol used to regulate data being sent over the wireless network, to avoid colliding with other wireless clients, which bogs down the wireless environment even more..
Assuming that you are the only user on your router, try booting into Safe Mode With Networking... Restart the computer and tap f8 until you see advanced boot options... Select "Safe Mode with Networking", then connect to your wireless access point, however it is you do that, whether it is through DELL proprietary software or Windows 7... If you cannot find how to view wireless networks available while in Safe Mode, go into Control Panel, click on "classic view", open "network and sharing center", on the left, click on "manage network connections", right click on the adapter you see, and click on "view wireless networks.. Find yours, connect and check the download speed, if it has improved...