Losing packets when pinging isp

Hi, my pc (HP Pavillion zv6000) is running super slow. I have Comcast as ISP, Windows XP with IE7, Belkin router connected wirelessly. My pc was fine one minute and then started slowing to a crawl and then started getting "page cannot be displayed." Called Comcast, they reset the modem on their end, then I powercycled all of the equipment and then checked the Belkin site to make sure router was still connecting and it was so I am back online but barely. I have been pinging google, yahoo and comcast and one time it will be "sent 4, received 4, 0 loss," and then the next time it will be losing 1 packet with a 50% loss and it just keeps going up and down like that. I am not that tech savvy, can anyone advise what might be happening or what to troubleshoot? It seems I get the worst pings when pinging comcast. Could they possibly be at the beginning of an outage? I would appreciate any help and thanks in advance! Kristi