okay, firstly changing the channel won't make any difference to the speed your surfing the net at, it might help the time it takes for the PC/laptop to register with the router.

To change the channel you just need to go into the router config pages, (usually accessed via the IP address of the router) on your web browser.

Een if its WPA your using for security, I still think its worth disabling security and then reboot your PC and see if it finds the router quicker next time to see if you still have the issue. You might have the same problem as I had but in reverse and find its better with WEP than WPA, i don't know. If its quicker with No security, then turn it back on and try the various different options on the router such as WPA, WEP 64, 128bit etc and see which one works quickest for you. Don't leave it with the security turned off though thats just stupid!