Older computers, Preventive hardware maintainence often required.

If you are interested in buying an older system, you need to be aware that often these systems may have bad capacitors or even a dead CMOS/PRAM battery. This can cause them to fail to start or if they do start, they may not work properly. You should look for bulging or blown electrolytic capacitors.

Most Lithium CMOS/PRAM batteries only run about 10 years before they die. Replacing the battery may be all that is needed. You can connect a two AA battery holder in and use standard alkaline batteries, if you have a place to mount such a holder instead of using coin cells or those Tadrian/Saft lithium 1/2 AA batteries that are used on many Macs.

If you invest into a computer with liquid Cooling (LCS)/Water cooling you will also need to replace old hoses and seals. The coolant can eat and destroy motherboards and cases. You need to fix these systems, preferably BEFORE they leak. They work very much the same as your Automotive cooling system.

Cleaning the machine is also a great idea too. Keyboards can get really cruddy.

Yellow plastic can be cleaned with VOL 40 Salon hair bleach from Sally's Beauty Supply as was suggested by another Youtube contributor.

I coughed and hit the Mic at one point and it made a cool sound. (grin) I was going to remove the effect but, I forgot where it was on the video. Let me know where it is, and I will run the sound through Audacity to remove it. Although, it wakes you up! (grin)