Dell Latitude Keeps Disconnecting from internet!?

No matter where I go, any library, public place, or friends home, My internet constantly disconnects.

When I lose internet, the network says "Limited Connectivity" and after maybe about 10 seconds or more, it's back, or it may not come back, or the Wifi driver shuts down completely and i cant get it back without restarting the whole PC (after a forced shutdown.) Very rarely will it give me a few minutes without interruptions.

I do not think it's the driver or the card, because I had the same issues with a wired connection tho not as bad, and that's two completely different pieces of hardware. Windows doesn't want to update them because they are already the "latest."

I noticed the less internet speed I have, The worse it is. I would do a complete OS reinstall, but I don't have the disk... I've messed with settings, turned off the hamachi network. Nothing's working...

-Dell Latitude D820

-Windows Vista Ultimate 64-bit

---Network Adapters

-Brodcom NetXtream 57xx Gigabit Controller

-Intel PRO/Wireless 3945ABG Network Connection

---Internet Connections(s)

-Everyone and their dogs...