interrrupts time placeholder on a7n8x-x

hi everyone

big problem with my configuration :
a7n8x-x
athlon 2200 xp
512mo ddr
gf4200
on my onboard ide channels are attached :
2 hdd
dvd-rom
dvd-burner
i also have a maxtor ultra 133 ide controller with
1 hdd
plxtor cd burner

windows 2000 pro (new installation with standart ide driver)
AND

when i'm burning, it took me 10 min to burn a cd at 24x (buffer underrun
used 228 times said nero)--- dvd burning end up with a buffer underrun

i've noticed a process called "interrputs time placeholder' eating almost
all my cpu time

also when i'm using nero infotools, my system restart immediatly

when i remove the raid card, everything worked ok, but this very
configuration worked perfectly ont my previous PC, so i want it to work
with my new mboard abd proc

can someone helps me