issue with unknown load

[Israel Garcia <igalvarez@gmail.com>]

I run  a debian lenny server (VPS) on a virtal machine for a log time
without any problem until today. The VPs stops responding early in the
morning and logs* from /var/log say nothing. I had to reboot the VPs
from dom0 console because there wasn't a any way to login in. Collectd
shows a superhigh load, cpu and memory few minutes before freezing.

I've  realized I have tools to know high load/cpu/memory  but I don't
know what was the cause of it
My question is:

How can I monitor which process cause this load on my Vps? I need a
tool that keeps this information.
Have debian some command tools where I can find what I'm looking for?

thanks a lot

-- 
Regards;
Israel Garcia