As we recall, the old computer was screwing up with the modern KDE interface. I had an old Athlon and a very old nvidia graphics card. It went flaky, and I tried everything. Finally, I gave up and prepared to get a new computer. I went to Amazon for everything, since they give me free stuff.
The first choice was the processor. I chose the amd a10 since this was reviewed as the friendliest to Linux graphics. It has a radeon r7 built in. That determined the motherboard, since it is an fm2+ socket. Luckily ammie had a gigabyte board on special and it was micro-atx, which is what I wanted.
I chose a m-atx case, which is ten times smaller than my old big case, and ten times lighter. The old case was bullet-proof! I chose the cooler master elite lan case because people said there was a lot of room. You don't realize how small these things are until you see them.
Amazon had a 500w atx power supply on special. The processor pulls 100w with a wraith cooler, so 500w is the minimum I would buy. If you are adventurous, you could get a m-atx power supply, but these are expensive. Also, I've never had luck with them. I like to go several times higher than the demand, because a flaky power supply is a terrible thing.
Commodity ddr3 memory. And I splurged on a 2.5 in 2 terrabyte disk, also on special. The old computer had an solid state disk drive, which I used, but this is a really fast disk.
The power supply is suppose to tuck in more, but it hit the wraith cooler, and would block any cooler, so I drilled a bit and made it stick out more.
I forgot everything I learned, and just assembled the whole thing before I powered it on. Blah. Nothing. Then full troubleshooting. Turned out to be a bad motherboard, which is the 99% chance. These things have a thousand solder joints, and have been made the same way since 1980. Ammie felt my pain, and shipped out a new one on express, and I returned the old one in the post.
Needless to say, it is all working now.
ps. the stupid new case did not come with the old 1980 pc speaker. Perhaps all the new cases leave this out. When I had the troubles, I stripped out (and fixed) the old speaker, and it was invaluable in determining a bad motherboard. When you get a new system, lay the mobo on the desk, hook up the processor and power supply, and short the power leads. The speaker should start screaming about the memory. Then put in the memory, and you should get the sweet beep of success.
pps - so quiet! I'll use this setup for the relative's media machine.
another note: Next time I would buy a processor without a stock cooler, and use a compact water cooler. The wraith cooler was too tall, and I don't think any standard cooler would work here.
performance: In uncompressing rar files, it's about 3 times faster.