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The operating system keeps a log of which files are needed at application start up and which data files are typically used (for example, a certain spreadsheet that is regularly used when Excel is booted). When the app is started, Windows XP looks at this list of files and seeks all of them at once. In so doing, it can consolidate disk seeks optimally and reduce head movement. So rather than thrashing the disk, application launch process now minimizes disk seeks.
To enhance this process further, Windows XP will moves the files around on your disk during lulls in computing activity. For example, it will reposition all files used in starting up your favorite browser and place them in contiguous blocks on the disk. This way, in just a few disk seeks, the entire application can be loaded. And to reduce head seeks even more, it places these blocks as much as possible on the outermost sectors of the disk, so that the heads have to travel as little as possible.
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Layout.ini is what keeps track of this....
XP keeps track of files used by every application. After several launches
of the same application, it has some sense of what files are required.
Thereafter, it uses an algorithm that says, basically, if a file has not
been used in the last six launches, it is marked for removal; if a file has
been used in the last two launches, it's marked for inclusion. Then based
on these notations, Windows XP determines which files need to be brought
into the block, and which ones moved out. When this move will take place
depends on several factors, such as how recently files were moved for this
application, and when the machine is available? Consistent with the idea
that disk activity should not interfere with performance, Windows XP won't
move the application files unless there has been no user-initiated I/O
activity for 13 minutes. Microsoft presumes this means the user is away
from the machine. It then begins migrating the files to the optimal place
on the disk.
Whatever you do, do not delete this file, can be a pain to recreate....