So, I have a 500GB HDD @7200RPM.
It is split as:
But I have begun to think this approach is flawed because if C:\ is formatted, I will lose registry values and stuff that goes in
%appdata% and so it is no use keeping programs in D:/ drive because they will be useless after all.3 Answers
Since it is only one disk you are using, it does not matter if you store program data in another partition. In fact, there would be no performance impact to just use one partition. In a single disk configuration, the sole purpose of partions can be seen in logical separation and/or for the need of other filesystems (say fat32 for data exchange with other systems in a dual boot setup).
3Install most programs on C (system partition) and keep data on other partitions. If you install programs on other partitions in most cases they still write data to the Windows registry. If you then format C and have a program on D after reinstalling windows on C it may not work because it can not find the data it stored in the registry. The only exclusion from that are portable programs.
I dont think there is much gain in performace. The only way to increase performance by partitioning on purpose is the so called short stroking:
There are two other reasons to make the case for partitioning your hard drive as you have described.
Backups. If you have the "minimum" (OS) stored on drive C:, then except for a few select files and folders it makes no sense to backup drive C:. If the bulk of your data and applications (X:\Program Files) are stored on other drive(s)/partition(s), then it is easier (for example) to backup drive D: and F:, then to specify many paths on drive C: to backup. Being easier to do backups means you might actually do them more often.
Failures. If everything is on drive C: and the drive fails, or the partition-table becomes corrupt, or the directory becomes corrupt, or the drive is accidentally erased/formatted (or erased/formatted by a virus), then everything not backed up is lost. If only the OS is on drive C:, and your applications and data are on another (physical) drive, then a failure to drive C: will not effect your applications/data. Even if the other drives are in other partitions on the same physical drive your applications/data are still protected from being lost in most cases other than a physical drive failure.
The disadvantage is that when partitioning the hard drive into multiple partitions/drives, there is the tendency to NOT allocate enough storage space on drive C: and when C: becomes near full, it can be difficult to have to shrink one or more "data" partitions to free up drive space to expand the space on drive C:.