First, there was the motherboard. Its integrated network card didn't want to go faster than 10Mbps full duplex, just out of nowhere. Great! Got it to the people I bought it from and they surprisingly said the "defect didn't show up". Ok, so they sent it back to me. Also surprisingly, it worked! So, it's not working, sent it to repair, they say they didn't do anything, got it back, installed it, fire up the computer, it works. Fine!
Few days ago S.M.A.R.T. said I should better backup everything, because my hard-drive will eventually die, but very soon. Fuck Win7, so I booted a Ubuntu Live CD, installed smartmontools, and checked the disk:
root@ubuntu:~# smartctl -H /dev/sda