Connection - Latency and Quality

I have recently purchased this computer, which comes pre-installed with
Windows XP Home Edition with SP2, and l am having a problem with my internet
connection to online Gaming and Private servers.

The problem l am experiencing is the Latency has increased from 250-275 to
now 300-325 and my quality of the connection has gone from a solid 100% to
now varying erratically between 92%-104%.

During gameplay (Nascar 2003) this causes others connected to the server
(any server) to disappear and the game to disregard my activity. I have
contacted my Internet Provider (Verizon) in the hope that they had a solution
to the problem, they tested my line and informed me that my DSL Connection
was performing correctly, and that they were aware of connection stability
problems with Windows XP and specifically the SP2. However, they will not
address 3rd party software issues, and informed me to contact Microsoft for a
solution.

I have also added Hardware, (SBLIve Card, Ethernet 10/100 Card and Also an
NVida Graphics Card) in the hope of trying to overcome the problem. Also, l
have gone through and disables many of the SP2 Features in the hope of
finding the problem area and trying to be more specific with what may be
causing it. Nothing has worked. Connection is still the same.

I would appreciate any help you can give me.