SuperFetch

Windows SuperFetch enables programs and files to load quickly.

When you're not actively using your computer, background tasks—including automatic backup programs and antivirus scans—run when they will least disturb you to save system memory space.

SuperFetch monitors which applications you use the most and preloads these into your system memory so they'll be ready when you need them. Windows Vista also runs background programs, like disk defragmenting and Windows Defender, at low priority so that they can do their job but your work always comes first. [source]

SuperFetch

SuperFetch is a technology that pre-loads commonly used applications into memory to reduce their load times, in a similar fashion to the preload in Linux. It is based on the "prefetcher" function in Windows XP.[8]

The intent is to improve performance in situations where running an anti-virus scan or back-up utility would result in otherwise recently-used information being paged out to disk, or disposed from in-memory caches, resulting in lengthy delays when a user comes back to their computer after a period of non-use.

SuperFetch also keeps track of what times of day that applications are used, which allows it to intelligently pre-load information that is expected to be used in the near future.

By default the necessary files are loaded into main memory, but using a feature called ReadyBoost, Windows Vista can use alternate storage such as USB flash drives, thereby freeing up main memory. Although hard disks usually have higher data transfer rates, flash drives can be faster for small files or non-sequential I/O because of their short random seek times. [source]

But some people disable this superfetch. Why? In Windows Vista and Windows 7 people tend to experience bad or good things about this feature. So better try with and without superfetch [source]

Goodluck!