Testing a PowerBook... suggestions?

If the PowerBook happens to come with AppleCare, you in luck. A continued warranty for three years from delivery. Also it will contain Tech Tools Pro, a good way to run a test on Mac hardware and software. If the PowerBook is less than 1 year old AppleCare is still available.

I'd run an extended hardware test and use that machine as my primary for the next few days, just to see what's going on.

As the other reply said, though, AppleCare should calm your nerves a bit. Make sure the seller transfers the agreement to you.

try everything. put in CD, DVD, etc, burn CD DVD etc. plug in all USB ports, firewire ports and whatever. try all network forms, wired and wireless. try out the modem if you actually have a way to do that. open and close it. put it to sleep, wake it up. reboot it. adjust volume and brightness. type. with all of the keys. yeah, all that. open programs, close programs, run as many programs at once as you can. if you can do all of this in the shortest amount of time as possible then you will probably be ok. and by loading the computer so heavily so quickly, you are likely to find out if there are any problems. also look closely at the entire screen to see if there are numerous dead pixels. . . you likely cant do anyting if there are only a few, but if there are more than a dozen or so and it is very noticable then you have a problem, but you are probably ok and wont find any problems.

do a hardware test with the disks that come with the computer. Also, as a poster said, bring techtool or diskwarrior along (if that's not being included in the sale) and test the computer.

This may help

Try out the 2 apps by Coconut Flavour. They will tell you when & where you PB was made (showing its age) & the quality of the battery (showing you how much it was used).

Its a guide and obviously won't help find any hardware faults.