This is all for those who try many operating systems at the same time... and those who want to test a dose of the newly released operating system...with out making any changes to your Master Boot Record or to your current system...
1) You don't need to worry about partitioning if you are not aware of it. Here you can specify any of your harddisk drives for the purpose of storage for the other operating systems... The guest operating systems will use the free space available in the windows without harming anything to your files...
2) You don't specifically need the installation cd/dvd of the operating system... an image file in .iso format will also do the same...
3) You can create the files in the guest and can restrict the amount of HDD occupied by them...
4) You can allocate no: of processors for the guest operating system out your dual/quad core processor...
4) You can specify the amount of RAM for the guest since this ...
so a lot of freedom and customization... no risks of careless partitioning....
For more details you can refer through these websites:
