Oh, sorry, I forgot to mention that my cable modem is connected to the onboard LAN.
But tried with the onboard one, and that didn't change anything.
The Internet works well with both LAN, although it is only a 8mbps connection.
But here is something new.
I tried to copy a 4.3GB file to the remote drive from my secondary disk (Samsung F2). It took 25 minutes to get until 85%, the speed was at 1.8MB/s, then I got the message:
Error, cannot read E:\folder\...\filename ... skip, retry, abort.
When I hit the retry I got the same message. Then, few minutes later the drive letters for both partition of the disk disappeared in My Computer. After restart they were back.
So I tried to copy from the primary drive, and experienced the slow transfer rate, as well. Few minutes later I interrupted the transfer.
After that I started to copy 25GB from secondary to primary drive. The speed was ok, but when it reached the 83% it stoped. Then again the same message that cannot read the file and the drive letters of the second disk disappeared.
Both serial and parallel ports were already disabled in bios.