Wierd stuff with a PPPoE connection

I don't know what the hell is going on. So I installed Windows 7 x64 built 7600, internet was working as normal, then suddenly it started to disconnect and get speeds of 200kbps. My connection has a 50mbit limit and so far it worked good on windows Xp.

My network card is a nVidia networking controller from a motherboard with an nForce 560 chipset on it Gigabyte GA-M56S-S3

I installed and reinstalled the drivers countless times, there was no change. I called my provider and they ran numerous checks, even calling me to say they solved the problem, but nothing.

So I disabled TCP/Ip v6 on the PPPoE connection and it worked pretty good (aprox 4mbits/s). After 1 week the speed dropped to an avarage of 1,5mbit/s. Today I changed the MAC adress of the network card and it went up to 5-6mbit/s (a bit more than the avarage 1 week ago). Could the MAC have anything to do with it? The MAC I put was random.

To make things more interesting, I plugged my Acer laptop which has windows XP and the internet speed is aprox 15mbit/s.

Sometimes I would get something like 200kbps download and 9,5mbit/s upload.

I searched on nVidia's website for the newest drivers, but the n560 series one says it didn't found any hardware for the drivers I'm trying to install.

I really want to resolve this problem withouth buying another networking controller and have a PCI slot occupied for nothing.

I have the Asus p5b-plus with the Atheros L1 gigabit adapter and I'm on Windows 7 64 bit. I was getting frequent disconnects when transferring large files over the network or downloading torrents. This required me to run through the troubleshooter each time to allow it to work temporarily again.

I fixed this by going into the driver properties panel> Advanced> Task Offload> Off. After it reset I was running fine.

I don't have that option in 'advanced' but I set the jumbo packet to 9012 or something like that.

This is crazy, I shut down windows because I left home when I came back same problem : 1,2mbit/s download and 9mbit/s upload. So I set the network adress back to none (default MAC) and I have 4mbit/s.