[jyl]

The three things that are easy to try/fix are (1) reload OS, (2) replace hard drive, (3) replace RAM.

You should first protect your data - sounds like you started that by putting the old drive in the USB enclosure. But, even if that old drive appears to be working, it can fail at any time - so you need to copy the key data from that old drive to a fresh drive, so it lives in at least 2 places.

Next, do (1) (2) (3) on the old laptop. Sounds like you've done (1) and (2). I wouldn't spend much money or time on the old laptop, not when you can buy a netbook for $300. Definitely don't screw around trying to diagnose motherboard problems, etc, on such an old machine. Your time is worth lots more.

Guys, pay attention to backups. My iMac is automatically backed up multiple times x day to an external drive. I've decided that's not enough, that external drive can fail, the house can burn, someone could break in. So I will be also backing it up 1 x month to a second external drive that I'll keep in the office (thanks to stomach and sapporo for their advice.)

Maybe I've had bad luck, but in my star-crossed experience hard drives start failing after 2-3 years - this is my last 10 years' experience across my PCs, my Macs, and the TiVo. Seems like I'm replacing at least one hard drive a year. And the hardware has a finite life. PCs last me 4-5 years. Macs last me 5-6 years. Seems like stuff "should" last longer, but for me it just hasn't.

Oddly enough, in the 1990s I seldom had a problem w/ hard drives failing. I don't know if that's just random/luck.