SYSTEM task it's eating my CPU!!!!

ok, so it happens to apear in the task manager a task named system (216 -
220 kb memoy using) and it takes all the procesor speed... what i mean is
that ussualy the inactive system poceses used to show 98 or 97 % of the
procesor usage but now when i look at the procesor monitor i see it is
always runing 100% and it increased mi CPU temp a lot!!! i've already
formated but i backed up my files cos i can't give me the pleasure of
erasing them, they are too important so what i need is find out how to get
this "virus-or-what-ever-the-fuck-this-is" out of my computer cos i can't do
any thing.... it keeps using all the CPU on this task and every thing else
is just secondary so as you can imagine,,,,,,,, every thing it's too damn
slow!!!!

resuming..... i need help guys... i really do.
could you help me?

DATA:

1)definetlly out of the question: erasing my files
2)done tons of scaning with noton (updated to today), panda and all removal
tools i cuold find (well not all of the but a lot)
3)i need to get my files cleaned up


while i don't touch my files, the system runs fine.... but then i had
downloaded winxp sp1 and that's one of the files i have saved in the other
HDD, so i run it.... and after restart BANG!!! the "sstem" task atacks again

PLEASE HELP

PC INFO:

AMD Athlon XP 3200+
1GB DDR 333Mhz
Mo-bo MSI
HDD seagate 160gb 10000 RPM

THANKS GUYS!!!!! ;-)