Low FPS in Joining AVI with VirtualdubMod

[Tatase]

Hi to all,
I bought a new PC, Shuttle XPC w/Athlon64 3200, 512MB DDR@400Mhz etc etc.
I installed VirtualdubMod from sourceforge and I need to join 2 avi files, sometimes Xvid, sometimes DivX5.
The problem is that if I join two Xvid (I have Koepi 1.00 build) I get about 2000 fps (obviously I select (direct stream copy), but when I append 2 divx I get more or less 150-200 fps.
I installed the free DivX5 codec from DivX.com.
The thing that makes me go crazy is that with my previous PC (2 cpu@866Mhz 256MB Ram) I used to get 1500-1700 fps. This because in direct stream copy the factor is the speed of the HD, and not CPU. What I don't get is why now Xvid is @2000fps and DivX is @150fps. So HD in my current configuration is not a factor.
Thanks for any reply.

Tatase.

[Tatase]

Sigh, no one ??