I haven't seen this posted anywhere yet so here goes:
Performance Counter Problems with VIA 686B and Intel 815x Chipsets in Windows XP
"In Windows XP, you may experience poor video capture and erratic System Monitor readings if your computer has either of the following chipsets:
Intel 815x chipsets with Advanced Programmable Interrupt Controller (APIC)
VIA 686B chipsets"
Performance Counter Problems with VIA 686B and Intel 815x Chipsets in Windows XP
"In Windows XP, you may experience poor video capture and erratic System Monitor readings if your computer has either of the following chipsets:
Intel 815x chipsets with Advanced Programmable Interrupt Controller (APIC)
VIA 686B chipsets"