I agree 100% with Howard. A reload from scratch is your only realy recourse for a stable system. To answer your question directly, nothing is required for event viewer to function except XP itself. No .net or service pack. Usually the cause of a blue screen is some sort of driver issue but it would seem you have much deeper rooted issues. In a true blue screen scenerion it will tell you in the text (near the upper right hand corner of the screen) which file the system had an issue with. Somethin likne ATIxx.sys or ntoskrnl will be displayed. Anyways, bite the bullet and reload, NOT REPAIR.
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Also based on your previous post about chaning the windows boot up and your splash screens, it's really hard to say what you may have done to the system.
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John