When you open a Finder window there will be the amount of space you have free at the bottom of the window. e.g. 6 Items, 188.38 GB available
It varies. It is dependant on the size of the hard drive fitted. There is no hard and fast rule.
Yes you can have the Mac OS on one drive and Windows on another drive. Or you can partition a single hard drive and have both on the same drive.
It will depend on what formatting system was used for the hard drive. If it uses FAT-32 format then it will work with a Mac but with the limitations associated with FAT32 formatting (file size/naming etc.). If you own the drive and are only using it with the Mac you can reformat it (using Disk Utility found in the Utilities folder within the Applications folder) as a Mac OS Extended (Journaled) drive.
You can rely on Mac system CD or a Mac Eraser to freely yet securely erase a Mac hard drive. See resources link.
Yes
To find the size of the hard drive on a Mac you can select the hard drive in a Finder window and then select Get Info from the File menu. Alternatively you can select About This Mac from the Apple menu (top left corner) and then press the More Info button. In the left hand pane select Serial-ATA to reveal details in the right hand pane. Bear in mind that formatting and structuring of the disc takes up space so, for example, a 250GB hard disc may only show as 235GB.
I'm not quite sure what you mean, so I'll give you both answers: "How do you use a hard drive for Mac and Windows on the same machine?" On a mac, insert a Windows install CD or DVD, and the computer will ask you if you want to set up windows to run alongside mac. In the process you will partition the hard drive, so you will kind of have a windows hard drive, and a mac hard drive, but on the same disk. "How do you remove a Mac hard drive and put it in a Windows machine?" I am not a technical expert, so you might want to look up "How to remove and install a hard drive". All I know is it probably won't fit, so you might need to buy a hard drive enclosure and run the drive from a USB port. Hope one of these helps! If not, please revise your question
Yes, as long the hard disk drive is not NTFS formatted.
Just drag the movie to the hard drive icon and it will copy it.
Most brands of hard drive will work with a Mac. If you want to run both Mac OS X 10.6 and 10.7 you will need to partition the drive and install a separate operating system into each partition.
You can learn to do Mac hard drive recovery at Disk Drill. Hard drive recovery can be tricky, but Disk Drill makes it easy and simple. They can help you get your data back quickly.
Any Firewire hard drive is best for a MAC. You can get either an empty one and install the software yourself or can buy the external hard drive with software pre loaded.