Since you are accustomed to AutoCAD LT, you might find another Autodesk product to your liking, called AutoSketch. It is primarily a 2D product but is capable of doing some simple 3D extrusions in the latest versions. It can produce and open DXF and DWG files and a few others in addition to its own SKF format. Version 10 runs about $300 to purchase, but copies of version 9 (which I use) can be found for under $100. It runs just fine on Windows 2000, XP, Vista, 7, 8, and 8.1
I tried Draftsight some time back, prior to purchasing AutoSketch 9, and it would not even launch without DLL file conflicts on the computer I had at that time (Vista), so I never got to try it out. I've heard good reviews of it, but sadly never got the chance to see for myself.