If your using XP and a nvidea card
and experiance the well known lockup bug when trying to play games  ect ect

the following should  fix the problem,

1. go to display properties\advanced\troubleshoot tab\then un check enable write combining

2.go to start\run\regedit\the to the following key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

create the following dword >  LargePageMinimum   set it to
ffffffff in the hexadecimal which will = 4294967295 in value  -- reboot

3.try setting the agp apeture to 128MB loacated in bios settings