Vista freezes for 10-20 seconds

hi everyone,

i installed windows vista ultimate x64. I have these annoying random freezes
for 10-20 seconds every so few minutes. I can move my mouse and everything
hovering over icons still 'highlights' them but when you click it nothing
happens. If typing a text you can't time anything. After the 20 seconds or so
it kicks bakc into actions and it's as if nothing happened. When vista is
working i can hear the hard drives working but the moment it freezes i don't
hear anything any more, when it kicks bakc into action i can hear them again.
I updated the drivers for my motherboard,vista and my graphics card , still
the same.
Here is some more info:

Asus A8NSLI (nforce 4 driver version 15.01)
AMD Athlon 64 3500+
2GB ram
GeForce 8800GTS (driver version 162.22)

i have 3 hard drives in my computer:
ATA disk 1: 100GB (this is for the vista installation)
SATA disk 2: 200GB
SATA disk 3: 500GB

These freezes are really anoying, it tried a few things after googling a bit:
- tried to disable NCQ, but it wasn't enabled
- deleted the following parameter in my registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Servic es\iaStorv

I found some threads here and the on the internet about this but no concrete
solution has worked so far. Can anyone help me out?

Thank you in advance.