Slow internet on XP pc, but not always

"Try to change the channel on your wireless router :
It might be that your neighbor just got himself also a wireless router that's interfering with yours.
Try channel 11, for example."

"You mentioned torrents.

In your torrent app try to put a maximum upload speed to a low value like 20kB/s.
Put it something like half of the maximum upload your Internet Service Provider gives you.

The torrent upload clogs your tubes because: The torrent apps are aggressive in terms of number of connections to do the upload/download and when they use all the upload speed, your request to read a page on the internet gets behind the torrents so the pages take longer to load."