Virtual Drive / Partition Vs. No Partition

By default a computer operating system will keep your documents in a defined Users folder. In Windows Seven this is under the C:\Users\%username%\...

But again, as a safety net it is always recommended that you store your files in a separate location--should your current operating system crash, or you get a Logical Hard Drive Failure (read here) you have a fallback option to browse your files. By doing so, you are certain that such files are not affected whenever you've had problems regarding your Main Partition.

A logical partition is a space in your disk allotted to be used as if an individual hard drive (the reason why it is also called a Virtual Drive). Technically you cut your hard drive into sectors and name them C:\ or D:\ and so on. Each partition, either logical or hardware partition acts as if it was hardware. All partitions are treated equal and are showed as "local drives" when you open My Computer, in Windows.

So back to having just one primary partition and no other virtual partitions, you cannot be self assured of all your backup files (which you might apparently place on the same disk) Think of it as a container, and the container has a lid. You can subdivide the container into two or more and have their own lids, so in case that the primary container has been sealed, you can still access your files from a different lid which can still be opened and is unaffected.

While some software and system errors can be fixed, some just can't. And the thing is, even when your computer told you that it encountered a really grand error and you find it inevitable to reformat, your files are actually unharmed in one corner. But they get deleted once you fix the system.

If you have a separate logical partition, you can always keep a copy of your files, or simply make it your working directory to save your files. Should your operating system collapse, you can just go and reinstall it but you get to keep your files.