James and Marslee: Thank you very much for your input. I
read (and have re-read) all. It seems very helpful.

This week I am going to try to install a new hard drive I
purchased yesterday evening. I will update this thread on
the outcome.

wrote
snip but comments noted
You can check whether your HD is faulty by using HD
manufacturer
software. There is a software called smartmontools, which
reports the
status of HD like spin up time, hour of usage and the
staus of
relocation sector etc. This software is quite accurate,
try it.

I believe you, but I came across what seems a very good
price for a hard drive yesterday. More below.

I would recommeded Segate since it is quiet and has 3-year
warranty,
and Western digitial has only 1 year. I dont recommed
Maxtor since they
fail frequently.

I think gateway 900 motherboard supoort only IDE, not
serial ATA. So
you can only choose IDE hard drive

I thought IDE and ATA were just different names for the same
thing.

Regardless, from Gateway's site, the specs on the old hard
drive say it is a Seagate with an Ultra ATA/100 interface.
These specs say nothing about a hard drive cache.

Also,buy HD in Best buy and circuitcity since they offer
rebate,

Yesterday from Circuit City I purchased a Seagate 100 Gbyte
(2 Mb cache) internal hard drive ("Ultra ATA/100" interface)
with a five-year warranty. With the rebates, it will have
cost me only $40 + tax. Caveat to newbies: Sometimes getting
the rebater to make good on a rebate is like pulling teeth.
I've never failed to get a promised rebate, though, in the
half-dozen or so instances of major electronic purchases
that offered sizable rebates I've had.

My current computer has only 128 Mbyte of SDRAM, so I'm
thinking if I want real improvement then I should double the
RAM.

and
they may sell it cheap on black Friday next week.

Office Depot said that, too. Oh well.

Q. Should I be concerned about the buffer sizes?
Yes, more is faster and better. Get a 7200rpm and 8MB
buffer HD.

Just curious, what error messages you got upon startup?

Most recently, it's said a few times it couldn't even find
the hard drive. I turn it off, re-start, and the error goes
away.

The error messages have varied a lot. I've become so
resigned (or lazy) that it's likely a new hard drive, or at
least it wouldn't hurt to replace the old one, that I
stopped taking any note of the errors.

If it's not the hard drive, I am prepared to slowly rebuild
this computer. I put in a new power supply about a year ago,
and I now vacuum out the casing twice a year (I have cats
who shed). I realize proper cooling is important to the
longevity of the electronics yada. I've studied the
internals and removed the floppy drives while cleaning it
out, so I am becoming more savvy on maintaining and building
my own computer. This after years of cussing computer
manufacturers such as HP and Gateway for a variety of ills
and/or the poor documentation on their machines. (Though I
think Microsoft's chaotic "engineering" is likely at the
root of the problem for many computer ills. Pardon my
amateur venting, though I do write as a much experienced
mechanical engineer. Or pretenses toward same.)

Reformatting and reinstalling all my software went
relatively smoothly the other week, and did help performance
a lot. So per internet suggestions, I am likely going to do
this once a year.