RE: Partitions...
A PC/laptop hard drive has tables in a hidden track at the beginning of it's storage space, & those tables include the total amount of storage space available -- that's a partition, & if it uses less than the drive's total storage capacity, additional partitions can be added until all of the drive's storage space is used up. So every hard drive, once it's formatted & set up for use with your PC/laptop, has at least one partition, but can optionally have several. Windows for the most part treats partitions as individual, separate hard drives -- in win7 Windows only shows & lets you work with entire drives in Device Mgr. & the Storage -> Disk Mgmt section of Administrative Tools -> Computer Mgmt.
Multiple drive partitions are useful for organization & maintenance, the same way it's easier, more efficient to have shelves in a closet or a bookcase, or maybe several smaller drawers in the kitchen rather than one, very big drawer. Multiple partitions are necessary when you want to install & use more than one OS [Operating System] on the same PC/laptop, where it keeps critical files separate for each OS so for example Windows doesn't try to use the wrong files & crash. And separate, often hidden partitions can be used by some software to store backup data, or by manufacturers to store the factory setup files or an out-of-the-box disc image for that PC/laptop.
Creating partitions is very simple & easy when you've got an empty hard drive -- you simply create the partitions one by one, assigning the amount of disk space you want that partition to use. Once you've got data on that hard drive however, things quickly get complicated, since none of the storage space on a drive can be used by more than one partition. If you want to make a partition larger, there has to be free space available to add to it, & that free space has to exist at one end of that partition -- it can't be separate, can't be somewhere else on the hard disk. You can make a partition smaller, creating more free space, BUT, if you take space away from a partition & that space happens to contain files, those files would be gone forever, so most software won't let you do that -- you have to move those files first or the partition software will do it for you. Now it starts to get even more complicated...
Files are not stored on a hard drive in a nice, neat order -- instead pieces of files are scattered all over the place. Defragmenting a disk partition can move your files to the start or beginning of the partition, so that you can then shrink the partition by reducing the amount of free space at the opposite end from where you've got all your files -- that storage space will no longer belong to any partition, & becomes unallocated. If you had a 200 GB partition & reduced its size at the far end to 150 GB, you'd have 50 GB of unallocated space at the end of that partition that you could assign to another partition. IMHO it get's too messy, too time consuming & error prone moving files from the starting end of a partition, &/or moving the start of a partition, e.g. in the above example having an existing 2nd partition absorb the 50 GB you just freed up -- I find it works Much better working with partition image backups instead.
You should do a full backup before you do anything to a partition, & you REALLY SHOULD do a full backup before you work with the starting end of a partition. Since you've already got a partition image backup then, rather than worrying about moving anything at the beginning of a partition, just delete it, restoring that backup wherever you want. I've got my hard drive divided up into 3 partitions, & I want to increase the size of the 1st partition -- I delete the 2nd & 3rd partitions, increase the 1st as much as I want, then restore the 2nd & 3rd partitions, adjusting their size as necessary during the restore process. Later on I decide I don't need the 1st partition to be that large -- I'm not using the XP Pro install that much any more -- so I defrag that 1st partition, reduce its size [shrink it], delete partitions 2 & 3, then restore them from backup, again adjusting their size in the process. Works the same way if I want to change partition number 2, but I've only got to delete & restore partition 3. Hard drives are coming back down in price, so when I buy a new, bigger drive, I restore the backup of partition 1 to the new drive, adjusting its size, then 2, again adjusting partition size, & then 3, restoring that backup so it takes up the remaining available space. But wait, SSDs are also getting Much cheaper -- problem is the drive I buy is smaller than the partition with the Windows install I want to put on it... the actual files will fit, but the partition itself is too large, so after a defrag, depending on backup software I either backup & restore, adjusting partition size in the process, or I shrink the partition to fit, then backup & restore to the SSD.
That said, working with the partitions on your hard drive(s) is still a time consuming pain, so using virtual disks instead is becoming increasingly popular. Virtual disks are single files that are treated as though they're physical disk partitions. Win7 allows you to create virtual disks in its .vhd format, & once mounted they'll show up in Windows' Explorer & your Windows' apps the same as the partitions on your physical hard drives. On the downside they're slower & don't back up so well -- you're usually better off to copy a .vhd somewhere else for a backup rather than including it in a backup of the physical partition where it's stored, though you can of course create a partition image backup of a mounted vhd, then if/as needed restore it to a newly created vhd or a real hard drive. On the plus side you can add or delete virtual disks at will without having to worry about anything else stored on the hard drive, & win7 will even let you boot to a vhd. They can also be useful for hiding &/or encrypting data -- Truecrypt creates virtual disks that are usually encrypted, & can even be nested, with one virtual disk inside another... you can have one Windows install, a Truecrypt encrypted virtual disk with another Windows install, & inside that another encrypted virtual disk with the Windows install you want to use -- the idea is that if anyone looks at your PC/laptop they see a regular Windows install, & if someone finds the 1st encrypted virtual disk with Windows & whatever software, they'll stop there, will not bother looking further.
