sp2 runs 10-20 times slower than sp1

I have tried twice to install sp2 on

vpr matrix 2.0 gig Intel D845BG mother board
400 MHz bus speed stepping 4
L1 data cache 8kb execution trace cache 12k
micro-ops
L2 cache adv transfer cache 2048 kb
512 mb ram dim ddr, mem speed DDR266, DDr,Sync
Bios 1/20/2003 ver P08
cpu type 0 family F, Model 2 stepping 4 rev F
features: mmx yes netburst yes
streaming simd ext yes ext 2 yes, ext 3 no

The update for sp2 completes ok, then system restarted I
get logon screen, select my id and wait and wait and wait
eventually I get a blue screen, then the start bar
appears, after a very long time desktop icons appear,
then after awhile icon text appears under the icons. I
have task bar set to hide.

To run I put cursor at bottom of screen and eventually the
start button/bar appears

The bottom line is everything works if I got hours to waste
while sp2 runs.

This mother board requires the Intel application
accelerator which was installed prior to sp2. Without this
utility installed under sp1 this is how the computer ran
very very very slow.

The first thing I tried was to reinstall the Intel aap
accelerator rebooted and powered off machine. On restart
still had slowdown.

I have researched all of the 'do this first items' that
have appeared in prior newsgroup threads on this group and
do not find a match. The CPU is not a Prescott problem.

This is the 4th machine I converted to sp2, other three ok
but this desktop fails.

I used system restore to go back to a checkpoint prior to
sp2 and this system works like a champ without sp2

I only saw one other posting with slow down and that
person's problem were not resolved in this newsgroup.

Any ideas????????? Thanks Ernie