Help with finicky notebook.

I have had an issue for quite some time now concerning surprise shutdowns of my system. I will be in the middle of a message, browsing, or a program, and it will simply shut itself down without warning or ceremony, so to speak.

I have felt for sometime that it was an issue either of overheating, or a hard drive related issue. It really seems to be most prone to shutdowns whilst running programs.

I run a Toshiba Satellite w/ Pentium 4 at 2.80 ghz, and 448 MBs of RAM.

I have also recently installed Speedfan, and here is what my S.M.A.R.T. rundown had to say:

"Your hard disk is a IC25N060ATMR04-0 with firmware MO3OAD4A.
The average temperature for this hard disk is 40C (MIN=29C MAX=51C) and yours is 37C.
Your hard disk's S.M.A.R.T. attributes are now being analyzed and a full report about the reliability, health and status of your hard disk is generated:
Your hard disk is not below any attribute threshold. This is good.
Your hard disk was never below any attribute threshold. This is good."

All values tested by S.M.A.R.T. beyond that point showed Normal, good, and very good, except for my "Power Cycle Count", which it informed me to watch because it was found to be at 97, rather than 99-100, as per normal.

Any advice will be greatly appreciated! I have already found so many useful tips just browsing through these forums.

run memtest86 on the memory. it could be a dodgy stick of ram . also checkthe temperature of the processor. that sounds like a full fat p4 and they can get hot in a notebook case.

Would it be prudent or helpful to perhaps direct a fan towards the outward vents to assist in the cooling process? Any ideas as far as that idea is concerned? And is there any other way to check mem sticks besides memtest?