LinuxQuestions.org - What is the best prebuilt computer for Linux? What's the best Linux 3D CAD app?

In the market for a prebuilt for my youngest brother so he can get away from Microsoft Windows XP which he too got a virus with. It's the same new virus that my oldest brother got through email. Apparently I sent it to both of them because the Linux distro I was using wasn't infected by it, but it was a nice transport system because I sent this email with this virus attached to everyone of my relatives announcing a reunion, so like over 270 Microsoft Windows users who don't have antivirus are hosed. (oops) I have 300 first, second and third cousins on my dad's side of the family and only 30 use Mac's.

So... he has this old pII gateway and I want to get him something that's harmless for a contractor to use with Linux. He uses cad programs to design houses because that's what he does for a living. Custom design and building homes. Now he can't take the constant problem of computer viruses and having to keep Norton updating, etc. Long ago when I lived in Houston, TX, I looked over Polywell.... and this is like a two-part question because I don't feel like explaining all over again for the Linux - Software forum here at LQ.org ...

So... Compaq, Dell, Gateway, HP, iBuyPower, Polywell, Sony, Toshiba ... ?

Apples are out, he never uses the iMac my next oldest brother sent him. He says XP is easier. I guess so... uh huh...... not! So this is why I'm asking. He wants to build something like dual-64 bit amd but he doesn't know how. The horsepower is for rendering the cad drawings. I told him I would do some research and find him a cheap alternative. Of course if building can be done by him with some instructions written by me and it's cheaper than premaid, I might go that route. I tried to get him to go for a rendering farm using 3D studio with a bunch of cheap computers, but he knows better than I did even though I used to work with render farms at a post production place that used Windows NT and AlphaServers along with 20 MS-DOS machines running the dos version of 3D Studio and some WinNT Workstation boxes running 3D studio Max. So you see the mentality that I'm dealing with. "One system will be faster than a rendering farm if it's fast enough". This from a contractor who builds homes. (I have a brother I want to trade with someone else... if only I could... ) I could get him 5 or 10 old systems, etc., you see where I'm going... anyway...

The second question is... what's the best cad software for designing homes, you know, architecture drawings, complete with all the little template pictures of tree's, sinks, and stuff you'd see in a blueline drawing? That can also render 3d with lanscape, sky, street, etc..