Just a more clarified build based on whats been discussed in the thread already:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i3-4330 3.5GHz Dual-Core Processor ($129.99 @ SuperBiiz)
Motherboard: ASRock H97M PRO4 Micro ATX LGA1150 Motherboard ($76.92 @ Newegg)
Memory: Crucial Ballistix Sport 8GB (2 x 4GB) DDR3-1600 Memory ($58.94 @ Adorama)
Storage: Samsung 850 EVO-Series 120GB 2.5" Solid State Drive ($67.98 @ OutletPC)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($52.49 @ OutletPC)
Case: Corsair 200R ATX Mid Tower Case ($57.99 @ Micro Center)
Power Supply: EVGA 430W 80+ Certified ATX Power Supply ($32.99 @ SuperBiiz)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($14.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 (OEM) (64-bit) ($87.79 @ OutletPC)
Total: $580.07
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-04-21 12:52 EDT-0400
1. Everything you hate about W8 is fixed with: http://www.classicshell.net/ (Install the OS, open IE, go there. download, install, continue the rest of your life normally)
2. It seems like AutoCAD doesn't have problems running on even first gen i3s, but those systems have a dedicated graphics card. I didn't include one here, because you may not need one as the integrated graphics seem to be able to run most of AutoCAD just fine, but if you try something like SolidWorks apparently it turns to garbage. If you DO find out you need a GPU, you can probably get a $110-120 GTX 750.
3. The motherboard has 4x USB 3.0 and 4x usb 2.0, so you should be covered, and the Case has 2 USB 3.0 ports on the front as well as headset and mic audio jacks.
4. An SSD will make the computer "feel" fast, install the OS to it and a few APPs and everything else to the 1TB HDD. You may even skip the HDD if you don't actually have that much stuff, but autocad files can get pretty big, so I can understand you wanting 2 TBs in your original post.
5. This is a pretty low heat system, so you don't need any extra fans besides the ones that come stock with the CPU and case.
6. The motherboard also has a VGA out so you can still connect it to your old monitor. If you get a new monitor, the motherboard also has HDMI and DVI out so you can connect it to those more modern connections as well. If you find you need a GPU like a GTX 750, it doesn't have VGA, but like Caeden said, you can easily get a DVI to VGA adapter, some GPUs and monitors even come with them.
7. Antivirus software isn't always a ripoff, the problem is ones like AVG, Norton, McAffee ARE ripoffs. A free one like Avast is pretty good, and you can set it to "gaming mode" and it basically never bugs you. MSE is actually fairly bad at protecting you from viruses/malware,
http://www.tomsguide.com/us/best-antivirus,review-2588-5.html