Weird pauses while loading

[Avengeance]

It seems like if I am playing a game or opening a program on my gf's comp the mouse freezes for a split seccond (and it does it like 5 times or so) so the mouse get chunky for a couple secconds. Also if I am in a game (wow) and someone logs onto the ventrilo server I am on, the mouse pauses for a seccond. Im not sure why it does that but it confuses me and I dont know why its doing it. Could it be from the nvidia SW IDE driver? Here are the specs of my gf's computer:

AMD Sempron 3100+
MSI K8NGM-V Motherboard
512mb PC3200
nVidia 6800 PCI-E
80gb WD HDD
Onboard sound/lan