Gonna need more info.
Give all the details you can about your hardware (computer setup, connection type, graphics, sound and network cards, etc)
What's a typical PING plot for you? Is it smooth?
Are you using the system or graphics memory cache feature?
Give Device Manager a look see. look for yellow !'s or red x's. Could be a problem with your IRQ's being shared between devices that shouldn't share.
Check out the sticky posts at the top of this forum. May give you some info and things to try.
Do a virus check. Then do it again in "safe mode".
