I am pretty sure there is something wrong with my desktop PC. I am running Windows 7 64 bit and I started having hourlong periods of time with a ping of 500-580 ms according to www.speedtest.net. After a week, the high ping became a constant problem and it's been like this for a couple of weeks now.
I tried changing the ethernet cable, using a wireless usb adapter and hooking up my laptop with an ethernet cable, and I still had 500+ ms ping while the laptop only got 50 ms(which is the normal speed here).
I tried disabling my firewall(Windows firewall with default settings), and it helped, but only to a certain point. I still get hourlong swings of high ping, but sometimes it actually goes down to 60 ms, which is all right. I updated the LAN drivers of my motherboard(Asus P7P55D-E) and it didn't work.