Cleaning the prefetch directory:
Do not do this, it will impair performance. The author clearly has no idea of how prefetch really works. Prefetch files are not shortcuts and unused entries will have virtually no impact on performance.

Clearing the page file on shutdown:
This will considerably prolong shutdown times. It is sometimes done for security reasons but has no performance benefits. In theory a hacker could access the page file and gain access to sensitive information. In practice this would be very difficult. Unless you deal with very sensitive data this is a waste of time.

Increasing File System Caching:
The registry setting IoPageLockLimit has nothing to do with file system caching. It’s actual function is now accademic, it has not been supported since Windows 2000 RTM. It was never supported on any build of XP or Vista. Even on older systems the settings mentioned by the author will accomplish nothing. The minimum and default was 524288 bytes. If a lesser value was set the default will be used.

References:
http://home.comcast.net/~SupportCD/XPMyths.html

Larry Miller
Microsoft MCSA