I've been a windows-user for many years, but now I'm starting to use OSX Leopard, little by little. But I need to run some Windows applications (specifically AutoCAD 2010). I know there are many alternatives (Parallels, CrossOver etc.), can anyone help me make a choice? I need speed, and a simple way of opening the same file with AutoCAD and with OSX applications.

I throw in a vote for VMWare Fusion with Unity mode enabled. I had bad experiences with Parallels, but things may have gotten better since I last used it. I use Fusion all the time.

VirtualBox was suggested to me as free_ware equal to commercial products. However, I have just been introduced to Apple/Mac, so I suspect that it will be a challenge to get any of these virtual machines working on a Mac. Over time I should get serious about this since it appears that the virtual OS can run from a USB drive, so perhaps this can conserve HDD space on the Macbook with a tiny HDD.

I'll give both VMWare Fusion and Parallels a try before I make a decision.

You can't use Windows Programs on OSX as they use .dmg files on OSX. The ways you have is to use Virtual Emulation Program as VMware or simply dual boot MAC with Windows with the bootcamp.

Sun's Virtualbox is what I use for Windows only software I must have access to in OSX. How it would handle AutoCAD is another question though, but with enough resources it should run OK.

I think dual boot would be most suitable for your AutoCAD installation, as although I don't really understand it, I'd be pretty sure its pretty intensive on resources and you don't want to be running something like that virtually unless you have massive resources to throw at it.

I have been using both OS on my macbook pro using bootcamp. It's not a hard thing to do. The benefit is enormous.

I did consider bootcamp when I purchased my imac, but having been using Virtualbox for the last year or so to run my essential windows software on my Linux computers I naturally just chose to use it on the imac again.

I only use it for my Autodata, and various GM software though. None of which are resource intensive. It actually runs faster virtually that it does physically running as well. lol.