Intel Application Accelerator and slow HD performance

I once had an Intel system P4 2+ GHz 256+MB RAM which was dead slow -
5 mins to boot XPHome and problems setting a pagefile - always had a
value to 0 MB and Windows used a temporary one.

Then I discovered IAA and the system went from being on on Valium to
being on Steriods. Booted in less than a minute and applications
similarly loaded much much faster.

Now am plagued with slow Seagate ST340015A HD performance on ECS
L4S5MG/651+(V5.0A) mobo with P4 2.4GHz/256 MB/XPHsp2, but after
installing SiS Mini IDE Driver 2.04a there is no noticeable
improvement. 40GB HD about a quarter full - says it is using UDMA5.
All seems OK in BIOS.

Taking hours to defragment (didn't really need, only a few percent
fragmented), I believe because the HD is just very very slow.

Drive is only 5400 rpm 12.5 ms seek but I have older drives running
say 98SE which fly in comparision.

XP system is well maintained and free of viruses and spyware.

Once XP has fully started performance is acceptable - the real bottle
neck seems to be getting data off the HD into menory.

Helpful comments welcome

jd