Falling off Internet with Windows XP and ADSL

I have an:

AMD K-6 2/300
160 Mb of SDRAM (PC66)
120 Gb 8 Mb memory Seagate Hard drive (7200 rpm)
Nvidia GeForce2 MX/MX 400 video card
Creative SB 512 Audio card
PCI Fast Ethernet Adapter 10/100 IEEE 802.3 10 BaseT ja Ethernet Card (RealTek 8139A)
Running Windows XP Professional
Broadband ADSL connection at 10/100
*********************************

I get on the internet and can stay on for a reasonable amount of time but then I fall off and can not get back on again unless I reboot. I even use a "Connection Keeper" (downloaded from Webattack.com) that seeems helpful sometimes but at other times.....I still fall off.

Is there some way for me to fortify my connection or make correct any errors that cause me to fall off?
I do network diagnostics and it only tells me the same thing...ISP unable to be contacted even when pinging...or their server is down....if that is the case why does an immediate reboot get me back on..if their server is down?

thanks
Jesse Jr.