Ammo - some good questions, and if 20 people replied, you'd have 20 different sets of answers!
I have built three AMD systems, so I'll tell you what I would do/have done.
ebgb is right - AMD processors run very hot, so if you're scavenging components from an old system, I would be sure to use a decent tower case with plenty of cooling fans. I made the mistake of using an old desktop case which originally housed a P2-266 processor. My processor was running at 67°! By using a modern case with two fans drawing air in through the front and two fans blowing air out of the back, the processor now runs at about 50° + or - a few degrees depending on ambient conditions.
Click
here to view the case I got - get one like it with the optional fans.
IMO, the best mobo you can get for an AMD processor is Asus - dsigned with AMD processors in mind. If I were to upgrade now, I'd probably get the AMD2100 CPU and Asus A7V8X mobo. I have been delighted with all the Asus mobos I've used, and their website provides excellent support. These components may not still be leading edge, but your mom won't mind. They'd even be good enough for AH. Some people have had issues with the VIA chipset and mobo drivers, and now err towards the N-Force chipset. All I know is that with my VIA boards, with correct mobo drivers installed, I've never had an ounce of trouble.
I use a dedicated SB soundcard in my PC, but my girlfriend and cleaning lady (two separate people - lol) have the Asus A7V333 board and use the onboard sound and say it's fine. Guess your mom would be happy with it too, so hold off the sound card purchase till after she's tried it out. As for the vid. card, the one I used for the cleaning lady build was the "64Mb ATI Radeon 7500 DDR AGP TV Out" - perfectly adequate, and inexpensive.
Asus A7V8X spec: Note, Asus supplies manuals for all its boards in .PDF format. Also available on the site are all BIOS updates. The new Asus boards have the "EZ flash" facility - BIOS flash program built into the BIOS, so no more buggering about with the DOS Aflash utitlity. You also get four USB2 sockets on this board. If I were building now I'd have USB joystick, mouse, keyboard - plus printer and modem of course. Optional USB expansion ports available.
One final note - it's vitally important to mount the AMD CPU cooling fan correctly! And they can be a squeak to get on. I use a screwdriver blade held between thumb and forefinger of each hand and press down the clip with the screwdriver blade. Don't mess this up!
ebgb - what would you use for cleaning dust off fans and other internal components?