I'm a bit puzzled by the following line in the log file you posted:
17:52:44 Processor info: Intel(R) Pentium(R) 4 CPU 1.60GHz (2399MHz)
Is your P4 processor really running at 2.4GHz? Normally the processor name string has the target core frequency hard coded in it. The line above suggests that the processor is a 1.6GHz part being run at 2.4GHz. Can you confirm whether your processor is over-clocked on your motherboard?
Separate from this, Microsoft has a number of hotfix patches produced after WinXP SP1 that involve updating the ATAPI.SYS driver to address various issues. For example, take a look at this Microsoft knowledge base article:
http://support.microsoft.com/default...&Product=winxp
Other than this, my gut feel is that your problem is somehow related to the SiS chipset on your motherboard. I don't suppose you have access to another motherboard with a different chipset (say, Intel) to compare with? Of course, if it turns out the problem is related to a chipset hardware defect, then your only solution would be to change your motherboard.
Just my random thoughts...