Allright i know what your talking about. It is related to the QOS Packet this also wont make much of a difference. You can try it and see if it does any change, I have t1 so i didnt see any difference under 1% but if you have cable it can make a noticable difference.
1) Click Start, Select "Run"
2) Type "Gpedit.msc"
3) Expand the "Local Computer Policy" branch
4) Expand the "Administrative Templates" branch
5) Expand the "Network" Branch
6) Highlight the "QoS Packet Scheduler" in the left window
7) In the right window, double click the "limit reservable bandwidth" setting
8) On the settings tab, check the "enabled" item
9) Where it says "Bandwidth limit %" change it to read 0
10) Click Apply and then OK
However this only works on XP Pro, Good luck