Has anyone tried running Linux from within Windows using Qemu or VMWare or Virtual Box ? or even through a USB drive?

I have couple of question for that:

1. Will I be able to access and manage files on my hard drive?
2. Will I be able to access and operate different hardware attached to my computer (eg. Scanner, printer,...etc) ?
3. In other words, will I be able to run Linux virtually almost as good as installing it? And what are the major difference between running Linux virtually and Installing it to the hard drive?

I just need to take my time and try the full features of Linux before merging to it, I find rebooting every once and a while to switch between the 2 systems to be very time-consuming.

Thank you in advance.

Well, I actually do the reverse by running Windows in Linux, but the same principles apply:
1. The Linux guest will be able to access any shared Windows folders using Samba, and you can drag and drop files between Windows and Linux. However, you will not have full access to all of your operating system files.
2. You have full access to any USB devices which you can attach and remove from the guest operating system in real-time.
3. Generally, yes. You will lose any access to 3D graphics, so I don't know whether something like Compiz would work under a virtual Linux guest.

Based on my Experience with DSL
I couldn't access the hard drive files, couldn't mount the hard drive at all, when I checked, I found that DSL Wiki stated that it's not possible to mount the hard drive cause it's a fake-boot using Qemu.
Is this exclusive to DSL only or is it a general rule that when hosting Linux in a Windows environment, it's not possible to mount the hard drive?
And is the hardware unmountable too?