OS is Windows 7 Ultimate 64
My router config shows the usual 4477kbps downstream, but pretty much every site loads extremely slowly. I tried downloading some stuff and the speed was ridiculous, say 800 Bytes/s to 3-4kB/s.
I've run full scans with Avast and Ad-Aware, which are my default antivirus/spyware apps. After they showed nothing I got Malwarebytes, which gave me 4 false positives (I already knew they were but even verified this online). HJT doesn't show anything suspicious. I scanned again in Safe Mode, again, nothing. No suspicious processes either.
I'm posting this from my MacBook, which is on the same connection, and the speed is normal. My deskop PC is connected via LAN cable, the Mac via WLAN. The cable is pretty new and there has never been a problem with it. I've even checked the router protocols for odd incoming and outgoing connections (TCP/UDP) but there wasn't anything out of the ordinary. Lots of port 53 going to/from my ISP plus whatever websites I had just visited.
I don't know what to do anymore.