WindowXP Problem

I have an Acer laptop Aspire 5100.
120gis hard drive,512 memory.dvd,802.11 b/g wireless lan,AMD 64 cpu.
My I.S.P. is Verizon,lately with I try to get me mail on the Verizon webite,the computer flutter's between yahoo,and back to Verizon.
I does this constantly,and so fast that I'm unable to tab the help menu.
I hope you can answer this question,as to why and how to get rid of this.
The computer has been give T.L.C. by myself,it hasn't been dropped,any liquids spilled on it,or anything that would harm the integrety.