I walked away from my computer for a couple of hours, tops, yesterday. I
came back to it and the display and mouse were frozen.

It's a 3.5 year old personal computer (Gateway, with a 20 Gigabyte, 5M Ultra
ATA hard drive). I ended up powering down, when starting up received error
messages and then a failure to reach the Windows display. I ultimately
struggled through a Scanddisk from a Dos prompt and was able to recover
most, but not all, my personal files, copying them to floppy diskettes (3.5
inch type). I shoulda been backing up at least once a month, but wasn't.
Anyone else procrastinating: Man, don't do it. Stop now. Back up your files.

A tech support person at Gateway said hard drives don't usually last beyond
five years. Some die at three years. I've found support on Usenet for this.

My computer's running again, but to thwart another massive crash, is it
worth putting in a new hard drive? I've got $80 to spend, and I figure a
nice one will run about that.

I installed a new power supply (that is, transformer) last summer. It's
power and so heat output aren't that different from the old one. It seems to
be working out fine. Otherwise, all else is original equipment.

My last computer was a Hewlett Packard. It "died" irrecoverably after only
thee years. The shop couldn't fix it, though maybe I took it to a lousy
shop. So this is very discouraging. Throwing away $800 every three years
ain't gonna cut it anymore. So I've had it with these big brand names. I'm
ready to build my own, and think at this point I have enough expertise to do
so. I'm certainly not going to throw money away on a shop trying to fix my
computer again. It seems to me much of the expertise involved in a
successful computer repair involves simply patience and persistence.

How about the CPU? Should I investigate replacing it, too?

All suggestions about whether a new hard drive is worth the investment and
the CPU are welcome.

TIA