connection droped and downloads are slow

[pa computer]

I have Windows XP Home and connected to cable. I have turned off the virus prctector and firewall in windows. I am using Symanted 8 firewall and antivirus. I've disabled my firewall and no difference in speed was noticed. I went to Kuhncom.net, my ISP, and got a second new cable modem, no difference. I have a HP Media center computer. I restored my computer to it's orginal condition still no progress. My e-mail and internet seem to work ok. My download speeds are slower than when I had dial-up. I'm at the point I don't know what to do. Help if you can.